1. A method of "measuring strips" for the investigation of the sap exudation of crops under field conditions is described. The quantity of liquid exuded from the detopped stem stump is determined from the length of a wetted zone of a narrow strip of filter paper protected against evaporation of the liquid by a polyethylene cover bag. The strips with the cover bags can be used even to collect greater amounts of exudated liquid.
2. Using this method, the sap exudation of detopped maize plants was observed during the whole growing season. On typical curves illustrating the course of the wetting of the measuring strips, the temporary absorption of the sap from the cells and conducting elements severed by the cut, the lag in exudation and the actual sap exudation can be distinguished.
3. The length of the lag period indicates the magnitude of the momentary water deficit of the investigated plant and the rate of sap exudation indicates the availability of soil moisture.
4. The rate of sap exudation reached its maximum at the end of June and then decreased gradually. In this period also the distinct lag periods were first observed. The occurence of shorter lag periods between the 5th and 29th July, i.e. in the shooting stage which from the standpoint of precipitation is critical for the height of yield, signifies that the critical stage probably coincides with the period in which the natural disproportion between available soil moisture and transpiration may become important.
5. During the period of long lags towards the end of the growing season, the measuring strips were fastened upon the plant stumps 24 hours after the decapitation. The "exudation after 24 hours" determined in this way indicates a significant decrease at the end of August when the soil moisture dropped to a value approaching the permanent wilting percentage.
6. The results have shown that the method of "measuring strips" permits an easy and sensitive evaluation of the water relations of maize plants growing under field conditions.

Decapitated seedlings ofLinum andPisum treated with TIBA paste either above or below the cotyledons, showed different morphogenetic changes especially on the epicotyl stumps, due to the differences in the correlations of their epigeous and hypogeous cotyledons respectively, these being also primarily responsible for the differing dominance of their shoot primordia.
At the earliest phases of germination, an antagonism between TIBA and IAA can be demonstrated on the first internode inLinum, which is usually very short, as well as on the petioles of thePisum cotyledons. The former could be enlarged only by treatingLinum seeds, even when ripening on the plant, with TIBA paste and the latter, if retained by soaking seeds ofPisum in a TIBA solution could be promoted by exogenous IAA. This, on the contrary, reversed the morphogenetic effects of TIBA uponLinum seeds.

Transpiration rates of leaf blades of irrigated and not irrigated spring wheat plants were studied in relation to the water content and growth changes in the test plants during their development. The applied irrigation stimulated the growth and slightly delayed the development of the test plants. It increased chiefly the water content and to a lesser degree the dry solid weight in the plant body. The quantitative and qualitative properties of the water content in the plant affected not only transpiration rates, but also the development of new and the dying off of old organs and tissues, especially of leaf blades. Transpiration rates in irrigated plants were markedly higher than in not irrigated plants. Mean transpiration rates of different leaf blades varied and were typical for each leaf blade. From the static aspect it was possible to express and even to explain some of the relationships and the heterogenity of the leaf blades on the same stem by the "Law of Zalensky". This involved mainly the mean values of growth characteristics and the investigated features of the water regime. On the other hand, from the dynamic viewpoint it was possible to divide the different leaf blades according to their transpiration changes into two groups. The first group includes the blades of the first to third leaf, the second group the blades of the fourth to sixth leaf and the ear. The capacity to control the water regime in the different blades is greatest at the stage of tillering, shooting and milk ripeness. During these developmental stages the marked decrease in transpiration, caused in the first place by a number of internal and not only external factors, was explained.

The effect of photoperiodic inhibition on the course of development was demonstrated by changes in the length of the sheath and the lamina, the lamina being more affected than the sheath. In a number of variants with different initiation of photoperiodic inhibition, an elongation or shortening of the sheath and the lamina of the three top leaves was observed compared with corresponding control leaves. The shortening occurred in leaves which developed beyond the normal number of the original bracts. This was the case with variants with very early inhibitions. Variants with later inhibition had on the one hand abnormally reduced leaves with imperfectly developed spikes, on the other hand elongated leaves whose length resembled that of ontogenetically younger, lower leaves. The suitability of the morphology of leaves for the investigation of the course of plant development is discussed.

The effect of CO₂ on the plasmatic structure of root-hairs of wheat and barley and the epidermal cells of onion was observed. The results were evaluated on living material with the aid of phase contrast. The root-hairs of barley and the epidermis of onion react to short exposure to an atmosphere of CO₂ by a cessation in the flow of plasma, a lengthening of the mitochondria and a rounding of the plastids.
When the influence of CO₂ lasts longer, it causes fragmentation of the mitochondria. In this phase the cells recover most quickly from the shock caused by their exposure to CO₂. When the plant is under the influence of CO₂ for too long a time, the effect is lethal. The root-hairs of wheat, which have mainly granulated mitochondria, reacted after only 40 minutes in CO₂ by a rolling-up of all the plasmatic particles.
This observation agrees with the results obtained on permanent preparations in the former work and leads to the conjecture, that by fragmentation of the mitochondria, the cell adapts itself to inhibited respiratory conditions.

A method is described for the application of the dry weight increment technique of photosynthesis measurement to plants with narrow leaf-blades (e.g. Festuca, Stipa etc.). A sample of leaf tissue is represented by the area of a frame filled with leaf segments placed side by side. The leaf segments 26 mm. in length are cut out from the leaves with a special punch; their number in the sample must be determined empirically for each plant species. In connection with this problem the authors describe the relationship between the intensity of photosynthesis and the number of segments in a sample.
The accuracy of the indirect determination of dry weight increment with the aid of control samples is maximally ±1% for ten estimations and 5% probability, which makes it possible to determine photosynthesis with an accuracy of ±10% when the assumed dry weight increment is 10%.

From photoperiodic experiments and an anatomic study of the shoot apex in the facultative short-day plantsPerilla ocimoides L. it was shown in all cases that gibberellic acid (GA) application did not accelerate flower induction. Between the development grades 2 and 4, GA caused a certain temporary acceleration which, however, completely equalised in a short period and plants of both variants SD and SD+GA flowered at the same time. Long day plants (LDand LD+GA) also flowered simultaneously with a certain delay. GA caused the total length of the plant to increase in both cases by more than a double, while preserving practically the same number of leaf pairs in variants under the same photoperiodic regime.

1. Differences in the net photosynthesis rate (PR) and in chlorophyll (a+b) content in leaves of different age in the leaf rosette of Nicotiana sanderae hort. were studied. The PR was estimated by two different methods, viz. the dry-weight and the gazometric method.
2. Highest PR and highest chlorophyll content (referred to leaf area) were found in the young but well developed leaves, i.e. the third and fourth counting from the top (a leaf of 20 cm.² area served as first leaf). These leaves are designated here as "photosynthetically mature".
3. The decrease in PR during leaf ageing was more rapid than that of the chlorophyll content. At a certain chlorophyll content (about 2.25 to 2.45 mg./ /dm.²) the rate of net photosynthesis drops to zero.
4. The PR is linearly proportional to the amount of chlorophyll (referred to unit area), independent of the position of the leaf in the genetic spiral. No substantial differences in the results were found on using two completely different methods.

An investigation was made as to whether the cultivation conditions of algae affect their respiratory metabolism. Chlorella pyrenoidosa (82), Scenedesmus obliquus (125) and Euglena gracilis (259) were cultivated both in a static and shaken culture.
It was found that shaking considerably affects the respiratory metabolism of algae. The shaken cultures, in contrast to the static ones, display a higher O₂ consumption and have mostly a different RQ. It is possible that the differences observed are due to accelerated development and ageing of the shaken cultures.
It thus appears that shaking is an important factor in cultivation which must be taken into account during growth of experimental material. The values of RQ found here to be about 1-3 point to the fact that anaerobic glycolytic processes can proceed even under fully aerobic conditions. The culture of Scenedesmus obliquus (125) appears to have a less adaptable metabolism and does not respond to environmental changes as readily as Euglena gracilis or Chlorella pyrenoidosa.

1. Suppressors were found in reciprocal crosses of some varieties of barley for the manifestation of recessive and dominant alternatives of the following characters: number of rows of the spike, presence or absence of glumes, character of awns and formation of the spike basis.
2. A proof of the existence of suppressors is presented merely statistically on the basis of segregation ratios in the F₂ generation, in the total F₃ generation and in the individual segregating progenies of plants from the F₂ generation and in the back crosses.
3. It was confirmed that the inheritance of the characters investigated is independent in spite of the fact that the segregation ratios are complicated by the participation of suppressors.
4. Separated cultivation of individual progenies from hybrid seeds formed on the mother plant was shown to be very suitable and efficient in hybridization experiments of this type.
5. The significance of the participation of the suppressors in the inheritance of the characters studied is pointed out with respect to the practical breeding of barley.

In the course of seven years, mutual compatibility relations in 16 Sweet Cherry cultivars, grown in Czechoslovakia were investigated. Successful pollinations were evaluated according to the percentage of fully ripe fruits. The results obtained are summarized in Table l.The fertility as well as the pollinating ability of the individual cultivars are recorded in Table 2.
It was found that the cultivar Emperor Francis, cultivated in this country, differs from the variety of the same name grown in Western Europe, belonging to another incompatibility group and thus being also of another genotype. It must therefore be designated as Emperor Francis B. It is incompatible with Bigarreau Noir de Winkler, belonging to incompatibility group II (genotype S¹S³).
All remaining cultivars investigated are mutually compatible. Therefore, when larger plantings of these cultivars are to be established, only the time of flowering should be considered.
Further, the conditions are discussed which may cause repeated incompatibility in one direction only. The probable cause lies in flower biology (i.e. the age of blossoms of maternal plant) not in genotypic constitution.

The authers compared taxon and organ specificity of proteins of several species of the familyViciaceae, using qantitative serological methods. Each organ possesses a defined organ specificity of protein characters, the species specificity being preserved. On the basis of the results obtained both methodical and more detailed ontogenic and phylogenetic assumptions and conclusions could be drawn.

The intensity of respiration and of photosynthesis were investigated simultaneously in sugar-beet leaves not detached from the plant. Several hours before the experiment the leaves had assimilated radioactive¹⁴CO2 whereafter they were placed into a normal leaf chamber for continuous gasometric estimation of the intensity of photosynthesis, according to the changes in the concentration of carbon dioxide in the passing air. At the same time, the specific activity of C0₂ was measured in the air that had passed through the assimilation chamber. From the values of the specific activity of CO₂ produced by the leaf in the dark the intensity of respiration in mg. CO₂ can be calculated.
It was found that sugar-beet leaves produce radioactive carbon dioxide when illuminated, both on the first and the second day after assimilation of labelled CO₂. During the considerable over-heating of leaves in the chamber when the gasometric method did not reveal anything but respiration a high production of¹⁴CO₂ could be observed radiometrically, corresponding to a higher respiration intensity. The authors explain this fact by the assumption that photosynthetic assimilation of carbon dioxide takes place simultaneously with respiration but the passive CO₂ balance in the gas exchange results in increased respiration, which actually represents the difference between the intensity of full photosynthesis and that of full respiration.
The production of carbon dioxide by whole sugar-beet leaves under illumination is no exceptional phenomenon under normal nutritional conditions.

During experiments with tomato plants (Solanum lycopersicum L.) var. Průhonické, the problem of the incidence of the virus disease brought about by temperature variations, as described by VOVK (1958), was investigated. The tomato plants were cultivated under aseptic conditions and all contamination was eliminated. The soil, the flowerpots and boxes were desinfected and the plants were irigated with boiled water. During the day, the plants investigated were kept in the greenhouse at the temperature of 12-35° C and during the night in a room at the temperature of 1-4° C. The control plants were cultivated in the greenhouse. No symptoms of the virus disease occurred, this being demonstrated by tests onNicotiana tabacum L. SAMSUN andNicotiana glutinosa L. Temperature variations did not influence the metabolism of the tomato plants so as to result in the virus mosaic in a healthy plant.

Photoperiodic experiments with the spring wheat Niva were undertaken to investigate the course of photoperiodic sensitivity and localization of the dhotoperiodic reaction in the ontogeny of plants. The long-day plant used, however, was not amenable to detecting a period during which a shortened day would be completely devoid of effect on the rate of development. Some data indicate, however, that a period of increased photoperiodic sensitivity can be defined which would correspond to the period of photoperiodic reaction of short-day plants. The results also seem to indicate that this period does not terminate abruptly but gradually passes over into the ensuing period when the day length affects the rate of development solely through photosynthesis. This effect is well marked when such indicators as the shoot apex development and earing are employed. The existence of this transition period at the end of the period of increased photoperiodic sensitivity and its connection with the shoot apex phase from initiation of spikelets to initiation of stamens must be verified by a long-term experiment under strictly controled conditions.
Among the criteria used to examine the course of photoperiodic sensitivity earing appeared to be most suitable as it yielded curves with definite, more or less marked breaks; the investigation of abnormities (in a classical arrangement), too, proved to be of value, as they indicate interference with the relationship between growth and development. Orientation data were also obtained by measuring plant size in a classical arrangement of the experiment. Analyses of the developmental phase of the shoot apex proved to be of least value in the experiments described here.

A characteristic feature of the effects of humic acids on plant growth is the stimulation of growth in length of the roots. This is sometimes explained as being due to the auxinoid nature of the acids.
The author has examined this assumption by testing segments of wheat coleoptiles and of flax hypocotyls. The growth of segments of both types remained unchanged in solutions of potassium humate in concentrations of 10^-1 to 10^-7 g./l. as compared with the controls in water.
A study was also made of the interaction of humic acids with auxins. The growth curves of segments in concentrations of auxin up to about 20 mg./l. (flax) or 50 mg./l. (wheat) were not altered by the presence of a 10^-1 g./l. concentration of humate in the test solution. With higher concentrations of auxin the growth of the segments in auxin-humate solutions was considerably greater than in solutions containing auxin alone. The effect decreased with rising concentrations of auxins (β-indoleacetic acid and α-naphthylacetic acid).
The auxinoid character of salts of humic acids in water solution was not established, nor was there any confirmation of competitive antagonism in the sense of the antiauxin conception.

In a previous communication (Bartoš, Kubín andŠetlík 1960) a method was reported, which makes it possible to measure the average rate of photosynthesis in a representative sample of a large number of leaves. The sampling is made by cutting out disks of leaf tissue, following a definite pattern. Isolated leaf disks are then illuminated under controlled conditions and the rate of photosynthesis is estimated by weighing the increment of dry matter in a given time interval.
Data published in the present paper demonstrate that this method can be successfully used for a characterisation of photosynthetic capacity (specific rate of photosynthesis, seeBartoš, Kubín andŠetlík 1960). Both specific values for individual plants and average values for homogenous plant populations may be estimated with very good accuracy. One of the chief factors which render this possible is obviously the surprising homogeneity of the photosynthetic tissue of leaves. Samples of very small size may serve as representative of a large total leaf area, e.g. of a population under field conditions.
Preliminary results of comparative investigations suggest that, with the plant varieties examined, differences in photosynthetic capacity are not very great, both between and within populations of diverse varieties. Differences as large as 50% have been encountered so far solely between values of photosynthetic capacity estimated for individual plants in a population. On the other hand, values of average photosynthetic capacity in populations of crop plant varieties within one species or genus are, as a rule, not very distinct and quite often no statistically significant difference can be demonstrated in such cases. Even if the varieties belong to different genera, differences in photosynthetic capacity in their populations greater than some 50% have been found only as an exception.
In considering all these results one important fact must be taken into account, i.e. the intensity of illumination in the apparatus. Contrary to what was intended and awaited, the radiation intensity used was not high enough to saturate photosynthesis in leaf disks. The light dependence of photosynthesis in isolated portions of leaf tissue apparently has a somewhat different character from that usually assumed for intact leaves of higher plants.

The term "equivalent evaporation power" is suggested to denote the evaporation power of the atmosphere measured as the relative evaporation from an evaporimeter which resembles to a great extent the physical conditions occurring during transpiration of a plant leaf (e.g. the Piche evaporimeter).
The height dependence of equivalent evaporation power at heights between 5 and 500 cm. in an "open area", in a field of sugar beet, maize, in a mature deciduous wood, in its small circular rejuvenation clearing and on a great clearing was investigated. The higher the absolute values of evaporation the lower the height gradient which is obviously observed to decrease progressively with height in all cases (Figs. 1 and 2). The stands decrease the average equivalent evaporation power in the height interval exceeding their height. Differences between the relative values of equivalent evaporation power of atmospheric environment surrounding different leaves of one plant are frequently considerably higher than those between ecoclimatically completely distinct localities (e.g. between a forest stand and a clearing).
A statistically significant positive correlation was found to exist between the gravimetrically determined all-day total of transpiration of seedlings ofFagus silvatica L. andAcer platanoides L., freely exposed in small lysimeters for the entire vegetation season and between the all-day total of equivalent evaporation power. For the number of days n=95 the mean correlation coefficient r was +0.58±3.0.031 for the beech and +0.56±3.0.046 for the maple. The regression coefficient, which is linearly proportional to the leaf area, was low and provides evidence for the biological regulation of transpiration.
It was shown by simultaneous measurements of transpiration (gravimetrically) of leaves ofSyringa vulgaris L. (n=95) and of equivalent evaporation power at the height of 10, 50 and 150 cm. above the ground in an "open area" that the height gradient of equivalent evaporation power of the atmosphere under natural conditions affects the intensity of transpiration at different heights (Fig. 3).
The observed facts are undoubtedly to be associated with the formation of the xerophytic or mesophytic character of leaves located at different levels of the same plant, and thus withZalensky's law.

1. The influence of varying concentrations of gibberellic acid on seedlings of wheat, lettuce and oats (up 10 days old) was observed and optimal concentration of 10 to 100 μg GA/ml. was established. Biometric evaluation of the experiments showed significant stimulation of the overground parts with all concentrations used (0.1 to 100 μg. GA/ml.) and significant inhibition of bhe roots with concentrations 1 to 100 μg. GA/ml.
2. For lettuce only the concentration 10 μg. GA/ml. was used. In this case, too, increase in length of overground parts was significant and inhibition of root growth was observed. For oats the stimulating effect of GA was recorded for both overground parts and roots.
3. Fresh weight of wheat was stimulated only by concentrations of 100 μg. GA/ml. In the case of lettuce (where values of fresh and dry weight were taken for the whole plant) we found a marked stimulation of fresh weight and a somewhat smaller increase in dry weight.
4. Observation of the dynamics of growth in length of overground parts and roots and increase or fresh and dry weight in lettuce showed a mutual relation between the values recorded in control and experimental plants in the period of 4 to 10 days following germination.

Results of the action of low doses of gamma irradiation, intensity 1-80 to 0-24 r/day, are recorded in this paper. Irradiation was carried out on a gamma field with a 0-50 g. equiv. Ra Co⁶⁰ source throughout the whole vegetative cycle.Trifolium pratense var. Jičínský was chosen as the experimental material. Growth and the yield of green matter was followed both on individually bedded out plants and on sown plots. Results of the measurement and weighing of the plants were statistically evaluated by means of the t-test and analysis of variation. Small, daily radiation doses (1.80-0.30 r per day) produced a significant stimulatory effect which was evidenced in the greater height of the irradiated plants as compared with the controls and a higher yield of green matter. In conclusion the paper deals with work that has already been carried out in this field. Experiments and measurements have shown that low doses of chronic gamma radiation are capable of stimulating plant growth. This work is confirmed by result obtained by Breslavets, Berezina and Shchibrya (1956) on other material.

1. Leaves of sugar-beet (Beta saccharifera), which had assimilated active carbon dioxide C¹⁴O₂, were subjected to the process of humification in soil. After three to five months of humification the dried soil was extracted with ether-alcohol, then with sodium or potassium hydroxide; the humic acids were separated from fulvic acids with hydrochloric acid. All fractions were radioactive.
2. Maize plants (Zea mays) grown in diluted Knop's solution with the addition of active humic acid showed radioactivity in the roots and leaves. There was, however, a marked difference between the roots and the leaves. While the activity of the roots after two to twelve days was about 100 to 200 cpm., that of the leaves was about 20 cpm. as calculated for one plant, or about 300 cpm./10 g. for roots and at the limits of measurement for leaves.
3. When a drop of solution and suspension of active humic acid was placed on the lower surface of the first leaf, it spread very little even in this leaf; the activity of the second and third leaves was at the limits of measurement after five days; the same applies to the roots.
4. Autoradiograms were fully in keeping with the results obtained with the counter. Roots were clearly marked and more or less intensely, while the leaves did not appear or appeared only as faint shadows.
5. These experiments do not resolve the question of whether unchanged humic acid penetrates into the cells. It can only be concluded, on the basis of these experiments, that if radioactive humic acid is added to water or to nutrient solution, radioactivity appears in the roots and later weakly in the leaves. If it is assumed that the activity measured in the plant organs was caused by humic acid applied direct, this means that it penetrates into the plant slowly, it is not accumulated and spreads throughout the plant slowly from the roots.

This paper presents a summary of new evidence for regarding sterility and dwarfing of oats (OSDV) as a virus disease. Brief references are also made to the identification of a further virus in Czechoslovakia-the wheat striate virus (WSV). Both viruses are transmitted by the leafhopperCalligypona pellucida F. The wheat striate virus differs from the oat sterile-dwarf virus in that it can be passed transovarially by the infected females of the vector to their progeny. This characteristic, which made it possible for the two viruses to be separated from each other, was demonstrated for the first time for pathogenic viruses on the European continent in this case. OSDV can be transmitted by leafhopper larvae and adults. The time during which OSDV circulates in the vector's body is very variable; it is usually three to four weeks. The incubation period of OSDV was three to four weeks for oats, four to seven weeks for wheat and barley; rye only showed retarded growth after four weeks. For infection to take place it was necessary for the vector to remain for a minimum of half-an-hour on the test plant; 100% infection was obtained when the vector remained on the plant for three days. The injury inflicted by OSDV on the host does not increase proportionately either with the duration of the feeding period or with an increase in the number of vectors on the plant. Concentrated extracts of the crushed bodies of infectious leafhoppers produced no symptoms of disease, when rubbed or injected into oat plants. Nor were attempts to transfer OSDV and WSV through soil or dodder successful. OSDV was, however, transferred by grafting. Both viruses gave rise to characteristic symptoms inAvena fatua L. andPoa annua L. These findings are discussed from the etiological point of view.

The paper describes a new strain of tobacco mosaic virus which has been named S-strain of TMV because of its characteristic stripe symptoms. The Al-strain of tobacco mosaic virus was used as the initial material.
In contrast to methods used hitherto the S-strain was obtained by interfering with the metabolism of the host plant by a change in the environment. (SvobodovÁ 1954, 1958). The usual hosts of tobacco mosaic virus were used, chiefly tobacco and tomato plants. These plants were cultivated under aseptic conditions on an agar medium in Erlenmeyer flasks with a reduced amount of nutrients, a shortened period of illumination and a limited air supply, so that they were stunted. Following the passage of the initial Al-strain of TMV through these dwarfed plants changes in symptoms appeared, which became apparent only after further passages through plants grown under normal conditions in a glass house in garden soil, where the virus once again had normal conditions for reproduction. Of the new symptoms obtained, only the most striking were further studied (the symptoms of S-strain). By means of alternating of the passage of the Al-strain of TMV from normal-to dwarfed-to normal plants grown under artificial nutrient conditions, i. e. a twice or thrice repeated sudden change of environment, the new strain (S-strain) was obtained five times in all and at different times of the year. From the symptomatic point of view no differences were found in the different repetitions of this change. The results were also the same for material from tomato plants and from tobacco of the Samsun variety.
The origin of the new strain was not caused only by the stuntedness of the host plants. It was also necessary to influence its metabolism by an abnormal environment (particularly insufficient air) in the Erlenmeyer flask before and after inoculation.
Following the reverse passage of the S-strain from plants grown normally in a glass house to dwarfed plants in an artificial environment no further changes occurred. Neither did the passage to ten other hosts grown normally on garden soil and in artificial nutrient produce any further change in symptoms. The S-strain has been maintained by a succession of continuous passages throughNicotiana tabacum Samsun for six years, and each year mass inoculation of a large number of plants is carried out. We therefore now consider the change to be permanent.
Indirect influencing of the virus through a change in the metabolism of the host plant sufficed for the induction of the new strain. Its symptoms appeared only after passage through normal unaffected plants, where the virus reproduction was not inhibited by the retarded growth of the host plant. There is a certain similarity in the emergence of the S-strain and the TM44-stram, obtained byPfanchuch et al., with X-ray irradiation. However, the initial material was the ordinary green strain of TMV.
The biological, chemical and other characteristics ascertained for S-strain and a comparison of these with the characteristics of the initial Al-strain and the ordinary green strain of TMV will be published later.

1. The relative suitability of three natural habitats ofGarex humilis was determined on the basis of dry matter production of individual plants at the end of the growing period. In the habitat which was found to be the most favourable from this point of view the lowest degree of ground cover by the plant concerned was also recorded. It is therefore possible "to assume that it is not only factors connected with the habitat that influence the occurrence ofCarex humilis under the given conditions.
2. A comparison of the course of the growth curve with changes in air temperature indicates that, for the initial growing period when soil humidity is adequate, temperature is probably the limiting factor.
3. The results of the cultivation experiments lead to the conclusion that the water factor has the strongest influence on growth in length and on increase in dry weight of the overground parts ofCarex humilis. Under the conditions obtaining in these experiments the influence of light intensity and of the chemical composition of the soil on growth were not found.

1. While studying the inhibitory effects of cadmium ions on the reproduction of tobacco mosaic virus in vivo it was found that a dose of 160 mg. Cd²⁺ applied in two waterings to one plant (immediately before inoculation and the third day following inoculation) produced an average 70% inhibition, without in any way injuring the plants themselves.
2. The inhibitory effect of cadmium ions decreased considerably when the plants were watered with a cadmium ion solution 24 hours before inoculation.
3. The differences in the course of primary infection, as followed by means of iodine tests, were particularly apparent in the following respects: starch is lost from the infected leaves of the experimental plants more slowly, the development of chlorotic spots is slowed down and their delimitation and structure are not so sharp.
4. On some leaves of young tobacco plants (N. tabacum Samsun) larger doses of cadmium produce spots, which resemble the necrotic lesions on leaves ofN. glutinosa following infection with TMV.
5. Preliminary determination indicates that cadmium ions cause a disturbance of phosphorus metabolism.
6. In the discussion it is suggested that the inhibitory effect of cadmium ions on the reproduction of TMV may, analogically to the conception existing in animal physiology, be connected with the interaction of zinc and cadmium ions in nucleoprotein metabolism.

Hemp (Cannabis sativa L.) was sown at intervals from November to August. For each sowing the time of flowering was recorded for male and female plants separately. Male plants usually flowered earlier than female. When the period of daylight exceeds 14 hours, that is when the days are lengthening in April, the female plants stop flowering and continue their vegetative growth. They start flowering again when the days are shortening considerably, in August, when the daylight period is about 15 hours. The male plants flower even when the day is longer than 14 hours.
In experiments during which the plants were shaded it was found that reduction of light intensity leads to an increase in the number of female plants, particularly if shading is carried out in the early stages of the plant's development.
The occurrence of intersexual plants was observed only during the short day period (11 to 13 hours), when they composed 22-30% of the total. When the day exceeds 13 hours intersexual plants no longer develop.
The grafting of plants of varying sex did not produce any sexual change-probably due to the fact that the period of vegetative approximation was short.

The authors studied the effect of the application of humus substances to the leaves ofBegonia semperflorens Link etOtto. For spraying they ušed a dialysed extract of garden soil containing sodium humate with admixture of fulvic acid in total concentration of 300 mg/l. Doses of 2 ml. were applied twice a week during the period of the main growth phase.
It was found that humus substances applied to the leaves cause a leng-thening of plant organs and increase of their fresh and dry weights. The chloro-phyll content and the amount of expired carbon dioxide are increased. The final result depends on the time when spraying was carried out and on the concentration used. It can be assumed that these effects are the result of direct influence by the humus substances and are not due to the action of stimulated soil or root microflora nor to improvement of the physicochemical character of the soil environment.
In conclusion we may say that humus substances applied to the leaves cause lengthening of the plant organs and increase in their fresh and dry weights. Chlorophyll content and the amount of expired carbon dioxide are also increased. The final effeet depends on the period of spraying and on the concentration used. In view of the fact that these effects do not differ from the effects caused by humus substances given as a part of root nutrition, we may assume that they are the result of direct action of humus substances and not of the action of stimulated soil or root microflora, nor to the improve-ment of physical or physico-chemical character of the soil environment.
A prerequisite for the practical utilization of humus sprays is, however, the extension of experiments to a greaternumber of plant species, the determination of their sensitivity, suitable concentrations of the solutions and the most suitable time of application.