The mechanism of the cytomorphological effects of low temperatures was studied by the fixation of young leaves ofTriticum vulgare with temperated alcoholic fixatives. Some specimens were plunged into liquid nitrogen, allowed to thaw and fixed; other objects were plunged into liquid nitrogen and fixed without thawing; control objects were fixed directly. At various temperatures of fixatives (-76, -27,+27,+58° C) different results were observed on the objects pretreated in the same manner. It was thus demonstrated that the destruction processes occur, in this case, during thawing.

The aim of this work was to establish under what conditions the water deficit values obtained byStocker's (1929) method can be considered to be those for actual water deficits. It was found that the water intake of detached leaves is not necessarily due only to incomplete saturation of the leaf tissues with water, but that in young leaves it is caused to a great extent by their extension growth. Thus, water deficit in the sense ofStocker's definition is not merely a simple physiological state of incomplete saturation of the tissues, but is expressed by the sum of the need for water to achieve the greatest possible saturation of the tissues and the need for water in the normal course of the extension growth of cells.

Within one leaf blade there are considerable differences in hydration of its parts. Marked longitudinal, transverse and area gradients of the osmotic pressure of cell sap were ascertained within the leaf blade of sugar beet. The osmotic pressure was determined indirectly by the refractive index according to the empirically established correlation refractive index: osmotic pressure (measured cryoscopically) cf. fig. 1. The gradient from the base of the blade to the tip ranged around plus 40% of the osmotic pressure at the base. This and other gradients mentioned were not noticably changed even when the leaves were artificially saturated with water or when water deficit arose or was adjusted by actual changes in the water balance. (In all these experiments the polarity of the transpiration stream was maintained.) The stability found in various degrees of hydration of individual parts of the adult leaf blade indicates that the variability is a result of the previous ontogenetical development of the leaf as a polar organ and of the fact that the adult leaf remains essentially unchanged by the actual changes in the water exchange. The heterogeneity found in the leaf with regard to the values here dealt with is an expression of the physiological heterogeneity of the leaf blade. ation intensity is concerned, it has been theoretically established that only after the reduction of turgor to nought does increased osmotic pressure of cell sap start to act as a factor in reducing transpiration, and that this reduction is under normal conditions comparatively small (Renner 1915, Stalfelt 1956).

1. Attention is called to the possibility of using resoroin blue for the staining of pollen tubes within the style tissue and the method of staining is described.
2. In pollen tubes, the growth of which is inhibited due to incompatibility, there is at least twice the amount of callose relatively to their length as there is in normally growing compatible tubes. In apple this is primarily due to the greater length of the callose plugs, in tobacco also to their greater density.
3. The regularity of the formation of callose in pollen tubes increases with the rate of their growth.
4. It is suggested that the physiological basis of callose formation consists in the limited capacity of pollen tubes to use the pyran components of metabolized saccharose in the process of respiration.

We have confirmed data regarding the action of γ-hexachlorcyclohexane as an agent inducing polyploidy, established a simple method of its application, determined the extend of its effect and found out whether it would be possible to replace the colchicine technique by a more accesible method of γ-HCH application. The method resulting from preliminary experiments with onion and lettuce was later applied to species and varieties of a number of plants (see list). The activity of γ-HCH as an agent inducing polyploidy was confirmed by the experiments. A method of sowing seeds in a damp film of γ-HCH was projected forLinum usitatissimum, Viola tricolor maxima aLactuca sativa. It seems probable that the use of γ-HCH instead colchicine pretreatment will be possible in cytological technique.

Phosphatase and catalase activity in the woody tissues of grape vine cuttings (Vitis vinifera), stimulated by β-indolebutyric acid, was studied at various temperatures. Its influence is evinced by increased root formation. The cause of the final effect is not, however, only quantitative acceleration of the metabolic processes. The parallelism of the activity changes of both enzymes in the stimulated and control tissues is evidence of this.
β-indolebutyric acid significantly increases the activity of phosphatase and decreases that of catalase.
I wish to thank Prof. Dr. S. Prát for his interest and help. I am indebted to J. Oplt for help in connection with the glass house experiments.

In the course of experiments with leaf samples of pumpkin, sunflower, leafy fodder kale, sugar beet, tobacco, clover and begonia several, methods of storing material were compared with the object of determining the amount of chlorophyll (a+b) after 1 to 3 months. Chlorophyll analyses checked by paper chromatography provided evidence that the most reliable method of serial analyses is the following: Leaf discs are heated in very pure anhydrous acetone to its boiling point (with some MgCO₃ present), rapidly closed with a paraffin stopper and then kept in the dark at temperatures just above 0°C. 50 leaf samples can thus be prepared for storage within 30 minutes. The decrease in total chlorophyll (a+b) content after 28 days of storage does not exceed 5%, after 84 days of storage 10% of the initial value. Chemical conversions of chlorophyll take place here which do not appreciably affect the spectrum of the acetone extract. The method cannot be applied to plants with acid-reacting cell juice (begonia, red varieties of fodder kale and the like). Other practicable methods of storage (a different storage in acetone, storage of fresh samples at +2 to +3°C, drying at +50°C, storage at laboratory temperature) bring about more serious destruction of the pigments.

Parallel measurements of the osmotic pressure (cryoscopic method) and the refractive index of cell sap were carried out on 246 samples from seven plant species. At the same time both values were ascertained as well as their relation for aqueous solutions of some sugars, organic acids and inorganic salts. The relations found with these model solutions are different for different substances. The quantitative composition of osmotically active components of cell sap changes in the course of ontogenesis and as a result the relation of refractive index and osmotic pressure also changes. By this comparison it has been shown that a reliable and more or less linear relation of the two values, which is advantageous for practical application, is only valid for a limited period in the ontogenesis of the experimental plant. The determination of the osmotic pressure of cell sap from the refractive index, the main advantage of which is its quickness and the small volume of sap required (0-02 ml.), is reliable if we construct empiricallyad hoc the appropriate correlation graph for the experimental plant for a limited ontogenetic period.

The work presented in this paper was a study of the influence of different isolated humus substances when applied to the overground parts of plants by spraying on the leaves. The humus components employed showed varying effects on growth, respiration and chlorophyll content inBegonia semperflorens Link et Otto. The result of the physiological changes is reflected in morphological changes of the overground parts and particularly in the structure of the root system. Fulvic acids were found to be the most effective of the humus components when sprayed on leaves.

The author has studied the relation of the catalase activity in thermal blue-green algae to temperature. Experimental data were taken from the first phase of the reaction, so that oxidation of the enzyme by the substrate was eliminated. The relation of the activity of a homogenate of thermal blue-green algae to temperature gives a curve similar to that obtained bySizeR (1944) for pure enzyme preparations isolated from beef livers. The resistance of the enzyme to high temperatures is the same in thermal blue-green algae as in mesopholic seaweeds. The catalase of thermal blue-green algae does not exhibit any special characteristics differing from the catalase of mesophiles.

In der vorliegenden Arbeit ist der Einfluss der äthanolischen Fraktion des Bodenhumus auf das Gleichgewicht der Glycide in isolierten Blättern von Weizen (Triticum vulgare Vill.) Lindě (Tilia cordata Mill.) und Rosskastanie (Aesculus hippocastanum L.) studiert worden.
Es wurde festgestellt, dass die äthanölloslichen Humusstoffe eine Herabsetzung des Gehaltes an nicht reduzierenden Zuckern in den Blättern der Versuchspflanzen und eine Erhöhung der Kohlendioxydausscheidung bewirken. Weil die CO₂-Ausscheidung weder dem Abnehmen der nicht reduzierenden, noch überhaupt aller Zucker entspricht, ist es notwendig vorauszusetzen, dass die äthanolische Fraktion auch andere Umsätze der nicht reduzierenden Zucker unterstützt, welche deren Abnahme in der Blättern bewirken. Ein emfindlicher Indikator des Einflusses der äthanolischen Fraktion ist die Grösse des Verhältnisses N: R (des Verhältnisses der nicht reduzierenden zu den reduzierenden Zuckern), dessen Wert herabgesetzt erscheint.
Ein Versuch mit Kaliumhumat zu Vergleichszwecken zeigte, dass diese Fraktion auf die Pflanzen anders wirkt. Sie setzt den Inhalt der reduzierenden Zucker herab, während die Menge der nicht reduzierenden Zucker eher erhöht wird. Die Atmung erscheint nach 8 Stunden des Versuches nicht wesentlich verändert.
Die äthanolische Fraktion sowie Kaliumhumat erhöhen die Aufnahme von Glukose aus der Lösung durch die Blattstiele der Pflanzen stark.

Der Einfluss der Alkohol-Benzen-Fraktion, der Fraktion der Huminsäuren sowie der Fraktion der Fulvosäuren, die in Konzentrationen von 0,1; 1; 10 und 100 mg je Liter wirkten, äussert sich im Gleichgewichte der Glycide in den oberirdisehen Teilen junger Weizenpflanzen folgendermassen: Die Alkohol-Benzen-Fraktion bewirkt ein Absinken des Gehaltes an nicht reduzierenden Zuekern (N) und ein Ansteigen des Gehaltes der reduzierenden Zucker (R), sodass der Quotient N: R herabgesetzt wird. Dies lässt sich als Anzeichen einer Erhöhung der Intensität katabolischer Vorgänge erklären. Die Fulvosäurenfraktion dagegen erhöht dieses Verhältnis, sodass sich auf eine Erhöhung der Intensität der Synthese schliessen lässt. Die Wirksamkeit der Huminsäurenfraktion ist wenig ausdrucksvoll. Die Beobachtungen dieser Veränderungen korrespondieren mit den Aenderungen des gesamten Trockengewichtes auf solche Weise, dass ein von der Fulvosäurenfraktion bewirkter hoher Quotient N: R mit einem Zuwachs des gesamten Trockengewichtes verbunden ist, während es sein durch die Alkohol-Benzen-Fraktion bewirkter niedriger Wert keineswegs ist.

Some peculiarities of the development of wheat alternatives causing their winter-hardiness were investigated.
1. Prolonged vernalization of wheat alternatives (for at least 80 days) considerably accelerates their development after autumn sowing or after earlier sowing on an artificial short-day regime. Under these conditions the development of alternatives is normally slowed down considerably due to the short day. With rapidly developing vernalized alternatives the growing point is differentiated and shooting occurs in the autumn, which is reflected in the loss of their winter-hardiness.
2. Continuous illumination similarly accelerates the development of alternatives after autumn sowing. As a result of rapid development associated with a differentiation of the growing point and with shooting, winter-hardiness is lost.
3. Low temperatures bring about a change of the reaction of the alternatives to the short day. After vernalization such wheats can develop on the short-day regime. The alternative Noe requires 35 days for the reaction change to take place, the alternatives Česká přesívka and K 26191 require 45 to 50 days of vernalization. In a lesser degree this property may be observed even in spring wheats grown on the short-day regime.
4. The determination of the reaction toward day length showed that the period required is much longer with alternatives than with spring varieties. Thus with spring wheat Lutescens 62 the required period is 21 days, with the Noe alternative 45 days. The same Noe variety sown from vernalized seeds requires 24 days, i. e. almost one-half.

The metabolism of exogenous tryptophane (3. 10^-2M) and β-indoleacetic acid (3. 10^-2M) in extirpated wheat embryos was studied chromatographically and electrophoretically.
It was established that the external application of β-indoleacetic acid in wheat embryos leads to the formation of its complex, indoleacetylaspartic acid. Chromatographical demonstration of the components of the complex was made foliowing alkaline hydrolysis.
A complex compound also arises from exogenous tryptophane, which again frees tryptophane following alkaline hydrolysis. The assumption has been put forward that this is malonyltryptophane, reported by Andreae and Good (Dannenburg andLiverman 1957). The isolated finding of a further substance may be mentioned, which possesses similar chromatographic properties to those of the indole complex-ascorbigen. For reasons so far unknown, this substance has not been isolated again in wheat plants.

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. During the period from June 11 to August 6, 1957 IEP_M values were recorded for the meristematic tissues of growing points of apex buds of brachyblasts and for phloem and xylem of brachyblasts and growing spurs of apple varieties Transparent Yellow, Lord Lambourne and Watervliet.
2. For a period of 7-14 days before the morphological differentiation of growing points of flower buds the shift of IEP_M values towards the area of higher pH was observed. This shift was found both in the meristematic tissues of growing points and in the phloem and xylem of brachyblasts and growing spurs.
3. After reaching a certain limit a shift of IEP_M values back to the area of lower pH at the original level was observed.

This paper gives a description of a two-channel photoelectric planimeter for measuring leaf areas. It is based on the absorption of rays within the range 0.6 to 1.4μ. The flux of radiation is converted to electric signals by argentum sulphide photocells. The difference in the photoelectric currents from the measuring and control channels is amplified by a sensitive and highly stable d.-c. differential amplifier and is indicated by a meter which can be calibrated direct in area units.

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. Anagallis arvensis L. (im weiterenA. a.) besitzt eine niedrige Keimfähigkeit, aber lässt sich leicht vegetativ vermehren und pfropfen. Beim Pfropfen "auf die Flasche" ist die Inkubationsdauer kurz, minimal bis 8 Tage. Die Pfropfung "übers Kreuz", das heisst das Durchziehen des abgeschnittenen kranken Stengels durch eine Längsöffnung im Stengel, der gepfropft wird, ist nur theoretisch von Bedeutung.
2. Die Blüten gesunderA. a.-Exemplare schliessen sich bei Nacht. Die fransenförmigen Blüten bleiben länger geöffnet. Blüten mit reduzierten Blütenkronen besitzen nicht abfallende, Monate lang geöffnete Kronen. Bei uns beginntA. a. in der freien Natur gegen Ende Mai zu blühen, im Glashause, sobald die Tageslänge 12^1/2 bis 13 Stunden ausmacht.
3. Der Virusspiegel ändert sich in denA. a.-Pflanzen je nach der ontogenetischen Entwicklung der Wirtspflanze im Zusammenhang mit ihrer Periodizität. Zur Reproduktion des Virus kommt es erst, wenn die Tageslänge mindestens 12 Stunden erreicht hat. Die Viren dieser Gruppe können in den Pflanzen auch latent vorhanden sein.
4. Bei Liptovský Hrádok in der Slowakei haben wir eine FormA. a. mit kleinen rostrot gefärbten Kronen gefunden. Die ersten Anzeichen einer Erkrankung vonA. a. an Vergilbung traten bei uns Ende Juni 1957 und im Jahre 1958 erst Ende Juli in Erscheinung. Die krankenA. a.-Exemplare bilden keimfähige Samen nur in den unteren Kapseln, die sich vor der Infektion entwickelt hatten. Die Virose kann in der Natur einen entscheidenden Einfluss auf die Frequenz vonA. a. haben.
A. a., Stellaria media undVeronica chamaedrys können Indikatoren der Anwesenheit von Viren und Virosen aus der Gruppe der Akarpien sein (Stolbur, Vergilbungen, purple-top und yellow-top bei Kartoffeln).Stellaria media kann als überwinternde Pflanze, die selbst Fröste (mindestens-25°C) verträgt, eine Reservoirpflanze der Viren dieser Gruppe sein.
5. Zu Prolifikationen beiA. a., kommt es von September bis November. Zuerst werden dabei auch die Blüten, später nur die Blätter gebildet.
6. Die Fransenförmigkeit der Blütenkronen beiA. a., kann eines der ersten Anzeichen von Vergilbungserkrankung sein. Es tritt bei übertragung der Hexenbesenkrankheit der Kartoffeln, der green petals der Erdbeerstauden, der Phyllodie bei Kleearten und bei Plantago major in Erscheinung, sowie auch bei Pflanzen, die an bakteriellem Braunwerden der Stengelbasis leiden, sodann auch vorübergehend als mögliche Intoxikationsfolge der fremden Unterlage nach einer Pfropfung gesunderA. a.-Exemplare auf fadenförmige Kartoffelkeime.
7. A. a.-Exemplare, die sehr schwer an Virose erkrankt sind, blühen überhaupt nicht, verzweigen sich aber stark und bilden anstelle der Blüten Blattrosetten.
Verengung, Welligwerden und Anthokyanisierung der Blätter sind nicht immer charakteristische Kennzeichen für eine Vergilbungsvirose vonA. a.
Pfropfreiser krankerA. a.-Exemplare riefen beinicotiana glutinosa wahrscheinlich infolge einer heftigen Intoxikation und eines raschen Absterbens der aufgepfropften Pflanzenteile vonA. a. keine Krankheitssymptome hervor.
Pfropfreiser krankerA. a.-Exemplare bewirkten bei jungen Sämlingen v

Die Autoren bringen eine kurze Mitteilung uber Beobachtungen der sofortigen Veränderungen in den Zellen der Epidermis von Allium cepa durch Ultraschallwirkung. Als Beobachtungsmethodik dieser Veränderungen wurde die Fluoreszenzmikroskopie mit Akridinorange-Pärbung verwendet. Es werden vier Stadien der hervorgerufenen Veränderungen unterschieden. Auf Grund dieser Beobachtungen wird angenommen, dass die quantitative Ausbeute der Energie des Ultraschalles für biologische Vorgänge verschieden sein kann, auch wenn in den sekundären Vorgängen die Ultraschallwirkung entweder zum Absterben oder Überleben der Zelle führt. Aus zytologischen Beobachtungen wird auf kolloidal-osmotische Veränderungen geschlossen.

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.