1. Protein synthesis in pollen tubes ofNicotiana alata Link etOtto estimated by the incorporation of leucine-¹⁴C is linear over six hours of artificial cultivation after a short lag phase. 2-Thiouracil and other growth-stimulating antimetabolites of natural pyrimidines and purines, such as 6-azauracil, 5-nitrouracil, 8-azaguanine and 8-azaadenine, stimulate the incorporation of leucine-¹⁴C into protein. The intensity of stimulation of protein synthesis is associated with the intensity of growth stimulation by antimetabolite.
2. Synthesis of RNA is inhibited by 2-thiouracil (according to the incorporation of uracil-¹⁴C, orotic acid-¹⁴C and³²PO₄ ^3- ).
3. Chloramphenicol (25 and 250 ppm) decreases during a one-hour treatment of pollen tubes the incorporation of leucine-¹⁴C by 12 and 24%, respectively. The same inhibition is found in pollen tubes stimulated with 2-thiouracil.
4. Pollen tubes incorporated 2-thiouracil into RNA. Stimulation of growth by 2-thiouracil can be reversed with uracil or uridylic acid.
These findings are related to the present views on protein synthesis and the mechanism of the chloramphenicol effect especially with respect to the possible explanation of the stimulation of protein synthesis during a simultaneous inhibition of RNA formation.
Physiological resistance of pollen tubes toward RNA antimetabolites, the relatively low sensitivity toward chloramphenicol, the contradictory change in RNA and protein synthesis due to 2-thiouracil and, further, resistance toward actinomycin D (Tupý, Süss 1965) point to the stability of the complex of messenger RNA with ribosomes in pollen tubes.

Exogenous RNA is degraded under sterile conditions in solution to fragments greater than tetranucleotides which can be taken up by the tomato. The degradation and uptake are not equilibre at first. Equilibrium is established only after 20 hours. Fragments of high-molecular RNA are taken up more readily than those of artificially degraded RNA.
Isolated roots take up RNA fragments in the same manner as the whole tomato.

Changes in water uptake immediately following the application of high concentrations of 2-methyl-4-chlorophenoxyacetic acid (MCPA) into the root medium of whole plants ofPisum sativum andVicia faba were investigated potometrically under controlled conditions. It was found that concentrations between 10^-2 and 10^-5 m bring about a sudden, pronounced and lasting inhibition of water uptake. Its rate depends directly on MCPA concentration. At 10^-2 m, sudden inhibition of water uptake becomes apparent as early as 10 min after application. With decreasing concentrations the appearance of inhibition is retarded but the inhibition is still sudden and well-pronounced. The inhibition of water uptake observed after MCPA application to the root medium of whole plants agrees with the sudden striking reduction in transpiration intensity observed byAllerup (1964) after the application of similar concentrations of 2,4-dichlorophenoxyacetic acid. The presence of MCPA in the nutrient medium causes inhibition of water uptake even in cut plants. Its rate again depends on the concentration of the growth substance. The inhibition does not appear here as quickly and is not as sudden and pronounced. High concentrations of MCPA during application to over-ground plant organs do not bring about immediate inhibition of water uptake by the root.

1. Wasserextrakt aus zerriebenen BlattläusenBrachycaudus napeli Schrk. verursachte in Verdünnungen von 1∶9 und 1∶25 an abgeschnittenen und in die Extrakte gestellten Tomatensprossen Welkeerscheinungen, d. h. das Welken und Einrollen der Fiederblätter, das Welken der Blattstiele und der Gipfelblätter. Die Wirkung stärker verdünnter Extrakte und solcher, die durch den Bakterialfilter filtriert wurden, war schwächer.
2. Durch Versuche unter normalen und konstanten Bedingungen wurde festgestellt, dass Wasserextrakte aus derselben Blattlausart in Verdünnungen 1∶9 und 1∶25 eine wesentliche Hemmung der Wasseraufnahme und Transpiration der abgeschnittenen und in die Extrakte gestellten Tomatenpflanzensprosse hervorrufen.

The transmission of the carrot mosaic virus (CMV) by the aphidsAcyrtJiosiphon pisum HARRÍS,Cavariela aegopodii SCOP, andMyzus persicae SULZ was proved experimentally. It was observed simultaneously that CMV has a non-persistent character. CMV can be transmitted already 2 min after acquisition feeding by the aphidsMyzus persicae SDLZ andCavariella aego-podii Scop. When the time of acquisition feeding is prolonged to 4 min, CMV is transmitted also by aphidAcyrthosiphon pisum HAREÍs. The host range of the investigated virus wasalso determined and its transmission to 8 plant species, belonging to 4 families, was achieved. On the basis of studies of the vector virus relationship and of the host range, further proof was given for the different character of the Australian Carrot motley dwarf virus, theApivm virus 1 Roland and CMV. The experiments showed that preliminary starving of the aphids for 1 h increases their ability to transmit the virus by 3-3%.

Durch die Erforschung des Verlaufes der Winterruhe im Zeitabschnitt von 1954 bis 1959 konnten wir Ergebnisse erzielen, auf Grund derer man behaupten kann, dass die Aprikose unter den Bedingungen der Südslowakei im Verlauf des Monates August ins Stadium der echten Winterruhe eintritt und diese im Verlauf des Monates Dezember beendet. Unter diesen Bedingungen braucht die Aprikose 1200-1300 Stunden Temperaturen unter 6°C, um die echte Winterruhe zu überwinden. Von zwölf Aprikosensorten, die wir durch Abschneiden und Versetzen der Äste in Zimmertemperatur auf die Dauer der Winterruhe geprüft haben, trieb die Sorte "Ananas" im Vergleich mit den übrigen Sorten regelmässig um 6-10 Tage später aus. Diese Tatsache ist auch mit den praktischen Erfahrungen im Einklang, die bei der Haltung von Aprikosenbäumen unter den normalen ökologischen Bedingungen der gemässigten Zone gesammelt wurden, unter denen die angeführte Sorte im Vergleich mit den übrigen Sorten um 3-6 Tage später blüht. Nach der Ansicht des Verfassers kann man nicht von einer direkten Abhängigkeit zwischen der Dauer der echten Winterruhe und der Frostfestigkeit der Aprikose sprechen. Die Pflanze ist nach Beendigung der echten Winterruhe von Temperaturbedingungen in starkem Masse abhängig. Unter günstigen Temperaturbedingungen (ohne Temperaturschwankungen) sind die Apriklsenbäume fähig, Frösten bis zu -20°C zu widerstehen.

Mit Hilfe eines volumetrischen Mikrorespirometers (nachZurzycki) wurde die Atmungsintensität an Vegetationskegoln von Winterweizen in drei, den Übergang vom vegetativen zum generativen Zustand bezeichnenden Etappen der Organogenese bestimmt. Die Atmungsintensität bezogen auf einen Vegetationskegel, das Trockengewicht oder den Proteinstickstoff war in der 2. und 3. Etappe der Organogenese niedrig, in der 4. Etappe höher. Die festgestellten Unterschiede sind wahrscheinlich mit den anatomischen Veränderungen, die in den Vegetationskegeln im Laufe des Differenzierungsprozesses stattfinden, verbunden. Dies betrifft besonders den steigenden Anteil der sich streckenden zentralen Markzellen und die mit dem Beginn der 4. Etappe verbundene Differenzierung der Ährchenprimordien. Man kann annehmen, dass die Änderungen der Atmungsintensität mit der Induktion der Blühreife nur indirekt zusammenhängen und eher mit dem anatomischen Umbau des Apikalmeristems im Laufe der Ontogenese verbunden sind.

Antiserum against the X virus inhibitor was prepared by immunizing rabbits with the inhibitor antigen obtained in two ways: (1) ultracentrifugation of potato leaf sap in a Spinco L for 1 h at 40000 r.p.m., (2) ultracentrifugation and fractionation of the sap on a Sephadex G-50 column.
The antiserum is specific against the inhibitor protein and does not react with other proteins of the plant or with the X virus. Direct serological analysis makes it possible to determine in the potato leaf sap either the presence or the absence of the X virus inhibitor, to follow the degree of inactivation of the inhibitor due to various factors and finally to determine the relative amount of inhibitor in various cultivars and hybrids of the potato plant.
A detailed description of the method for determining the amount of the X virus inhibitor in the leaf sap from various potato cultivars and hybrids is given. The amount of sap required for analysis is very small (1-2 ml) which makes it possible to carry out analyses on individual plants. The duration of analysis is about 1 h.
The determination of the inhibitor amount in the potato leaf sap agrees with that of the inhibitory potency of the cell sap in 87.7% cases.

Investigations were made on the effect of exposing barley seeds to gamma-radiation (5-40 kR), alone and in combination with the application of zinc (soaking the seeds in solutions containing 5.10^-5-5.10^-1% Zn for 12 hours before sowing) on growth and on the content of tryptophan, indole auxins and gibberellin-like substances in seven-day plants. Radiation decreased both growth and the content of tryptophan (e.g. by about 53% at 30 kR), of indole auxins (by about 60% auxin in the zone of IAA on the chromatogram at 30 kR), and also the content of gibberellin-like substances (by about 67% gibberellin content in the zone of GA₃ on the chromatogram) of plants. The irradiation of standard samples of tryptophan, indolyl-acetic acid and gibberellic acid alone with many times greater doses (up to 1000 kR) did not lead to marked radiochemical degradation of these substances. It can be assumed that radiation damages the enzyme systems "synthesizing" natural growth substances in plants. The damaging effect of radiation on auxins is already displayed in the synthesis of tryptophan, which is inhibited.
Zinc interacts with the damaging effect of radiation on growth. Optimum concentrations of zinc (5.10^-3% Zn) counteract the effect of radiation, up to doses of about 12 kR, on the growth in height in 7-day plants so that it is equal to the controls. Normal content of tryptophan and auxin in the position of indolecetic acid on chromatograms can only be reached by the addition of zinc when the dose of radiation was not greater than about 8 kR, which is less than the influence exerted by zinc on the restitution of growth. On the other hand, the biosynthesis of gibberellin-like substances at the position of gibberellic acid on chromatograms can be restored by zinc to their original level to doses of up to 30 kR. The increased biosynthesis of auxins and gibberellins caused by zinc in irradiated plants is explained by the activation of the remaining and non-damaged enzyme systems carrying out this biosynthesis. The activation of the biosynthesis of growth substances by zinc will also contribute to the restitution effect of zinc on the growth of plants from irradiated seeds.

The influence of penicillin in concontrations of 8.3-10,000 IU/ml on algaChlorella pyrenoidosa was studied. Depending on temperature, the concentrations of 14 to 6,000 IU/ml have a stimulating influence on algal growth which may go as far as 1572% as against the control. The differences in temperature (15° to 18°C or 25° to 28° C) and in the concentration of mineral substances in the Knop solution employed do not affect the mode of action of penicillin, but affect the absolute production of algae whose maximum lies between 2,500 and 3,000 IU penicillin/ml.

The paper presents results obtained from studying the linkages of the Rf₁ gene causing the restoration of fertility of pollen in the T type of cytoplasmic sterility of maize with signal genes of the 3rd chromosome in the F₂ and B₁ hybrid generations. Crossing of the fertility-restorer lines obtained on the basis of T cytoplasm with signal lines carrying recessive genes of the 3rd linkage group was carried out during the coupling phase.
The data obtained on the linkage of genes indicates that the Rf₁ gene is located at the proximal end of the long arm of the 3rd chromosome between loci d₁ and ba₁. The linear sequence of genes and the map of their distances were determined on the basis of experimental recombined values as follows: d₁-26-Rf₁-16(?)-ba₁-42-sh₂.

Application of a 1% aqueous solution of 2-methyl-4-chlorophenoxyacetic acid at the three-leaf phase brings about abnormalities in the development of barley ovule. The most typical abnormality is the complete or partial abortion of the embryonal sac, disturbances in the orientation of the embryonal sac (associated with the development of an integumental excrescence) and concrescences of two or more ovules. The abnormal ovules remain mostly unfertilized, which can have a negative influence on the crop.

Senf- und Zuckerrübenpflanzen wurden in der Phase des ersten echten Blattes mit dem Herbizid Pyrazon (= 1-Phenyl-4-amino-5-chlorpyridazon-6) in der Form eines Suspensionspräparates Pyramin in 0,4% Konzentration besprüht. Nach 1, 4, 7 und 14 Tagen nach der Besprühung wurde die Respiration der oberirdischen Pflanzenteile mit Hilfe von Warburgs Respirometer bestimmt. Der Stoffwechselquotient (in μl des verbrauchten O₂ pro 1 mg Trockenmasse in 1 Std. ausgedrückt) war beim Weissen Senf, der gegen Pyrazon sensitiven Pflanze, im Vergleich zu den Kontrollpflanzen gesenkt. Die Senkung der Respiration war desto grösser, je grösser die Zeitspanne zwischen Besprühung und Respirationsbestimmung war. Bei der Zuckerrübe, der gegen Pyrazon resistenten Pflanze, sank die Respiration nur den ersten Tag nach der Besprühung, wogegen sie zu den weiteren untersuchten Terminen nur unbedeutend herabgesetzt war. Bei der Anwendung von schwach subletalen Aufwandmengen war der Stoffwechselquotient der Zuckerrübe 7 und 14 Tage nach der Besprühung sogar höher als bei den Kontrollpflanzen. Diese Unterschiede waren jedoch nicht signifikant.

Pure cultures ofChlorella pyrenoidosa (82) andScenedesmus obliquus (125) were grown in the nutrient medium according to Benson in the presence of 0.05m sugars or 0.025m sodium salts of organic acids. The density of culture was measured throughout the course of growth. Satisfactory heterotrophic sources of nutrition forChlorella pyrenoidosa appear to be galactose, glucose and acetate, whereasScenedesmus utilizes glucose, cellobiose and acetate. The growth ofChlorella in the light is enhanced by galactose, glucose, fructose, cellobiose and maltose, that ofScenedesmus by glucose, fructose, cellobiose, galactose, maltose, acetate and pyruvate. Soluble starch suppresses growth of both cultures. The role of the substrates is discussed. It follows from the results that the growth-promoting sugars and organic acids can act not only as a source of carbon during general carbon shortage but also as ergastic material. The mechanism of utilization of some organic substrates will be taken up in a subsequent paper.

Cresol red was found to be the most suitable of the six colour pH indicators tested for the colorimetry of CO₂ concentration within the range of 100 to 2000 p.p.m. In the region near pH 8-2 (corresponding approximately to 300 p.p.m. CO₂)this indicator is most suitablein view of its low unit concentration, although somewhat greater differences in absorbancy can be found on changing pH by one unit if an approximately six-fold higher concentration of thymol blue is used. For higher concentrations of CO₂ (pH below 7-5) phenol red is most appropriate. Tropaeolin 000 and aurin (rosolic acid) are not suitable. It is more convenient in spectrophotometry and colorimetry using filters with narrow spectral ranges to apply any of the above indicators in the green-yellow-orange spectral region rather than in blue radiation.
When the air to be measured is bubbled through a bicarbonate solution, an equilibrium between the CO₂ concentration in the air and pH value is established in less than 10 min for differences in CO₂ concentration from 100 to 400 p.p.m. Partial pressure of CO₂ and the experimentally established pH value are related by the altered equation: pH =α- 0-934 log P. The values of α at different temperatures were determined.

The relation of the M₁ root length and the frequency of M₁ chlorophyll chimeras to the sterility grade and to the frequency of M₂ mutants ofArabidopsis thaliana is demonstrated.

Wir verfolgten die gegenseitige Beeinflussung von in Wasserkultur gezogenen Hafers und Gerste. In den Experimenten wurde die mögliche Konkurrenz um Wachstumsfaktoren entfernt und es wurde die Rolle der Wurzelausscheidungen bei der gegenseitigen Beeinflussung des Wachstums und der NPK-Anhäufung in den Versuchspflanzen geprüft. In einer Variante wurde periodisch stets jeden zweiten Tag auf die Dauer von 6 Stunden die Nährlösung aus den Kultivierungsgefässen geschöpft. Nach 43tägigem Kultivieren wurde eine signifikante Wachstumsinhibition des Hafers und Stimulation der Gerste festgestellt. Im Einklang mit den Wachstumsveränderungen war der N- und K-Gehalt auf 1 g Trockensubstanz erhöht bzw. herabgesetzt. Dagegen war der Gehalt des gesamten P, hauptsächlich in den Wurzeln, beim inhibierten Hafor aus der Mischung höher und bei der stimulierten Gerste niedriger. Wir setzen voraus, dass die Veränderungen durch die Wurzelausscheidungen der mitgezogenen Pflanzen verursacht wurden.

Azo-coupling methods were used for demonstrating non-specific esterase in the wheat root in all parts of a transverse section, usually with the exception of the woody parts of the vascular bundle. The central cylinder gave a more intense reaction than the primary cortex and the rhizoderm. The reaction was not inhibited by dodecyl sulphate. A weakening of the reaction intensity was observed after application of AgNO₃. The Tween method did not yield reliable results.

Seeds of the beanPhaseolus vulgaris L. (Veltruská Saxa cultivar) were gathered gradually at different stages of development, starting at fertilization up to full maturity. Seeds were freeze-dried and the dry solid used for preparing extracts which were analyzed by immunoelectrophoresis for the presence of proteins resembling those contained in the cotyledons of a mature seed. Proteins from cotyledons of the first stages of development of bean seedlings were analyzed similarly.
After a preparatory period, approximately from the second-third seed development stage, there is a period of intense protein synthesis that characterizes cotyledons of a mature seed. These proteins increase in quantity and are differentiated in quality up to maturity when a single antiserum detected a total of 12. After germination both the quantity and number of these proteins decreases.
It was found that some proteins are metabolically more active, both during synthesis and cleavage. This holds e.g. for phaseolin during maturation, as well as during germination. In addition, phaseolin changes its electrophoretic mobility, which is apparently due to proteolytic hydrolysis of phaseolin molecules.
During the last phase of maturation, viz. dehydration of seeds, some new proteins suddenly appear, apparently synthesized from pre-formed peptide chains.
In the discussion the possibility is taken up that the beginning on the synthesis of specific proteins characteristic for mature seeds is the cause underlying the disturbances in the embryonal development of distant hybrids.

Peroxidase isozymes were studied in the case of two diseases:Tilletia controversa in wheat andPuccinia recondita in rye. The method employed was that of disc-electrophoresis on acrylamid gel. In the case of systemic disease (Tilletia controversa) no change was found in the isozyme pattern until a concentration of pathogen took place in the ears that began to form. Proofs are given that the new isozyme in unmatured ears comes from the pathogen. In the case of rye infected withPuccinia recondita a new isozyme was found; the latter does not originate in the pathogen, its origin is being discussed.

The vessel member length-diameter and perforation plate-vessel member length relations inDioscorea alata L. have been investigated. The two types of vessel elements, one with scalariform perforation plate and the other with foraminate perforation plate, have been considered for correlation tests; the variables being vessel member length and diameter, and vessel member length and perforation plate length. Significant positive correlation was found only in the case of perforation plate length and vessel member length for types with scalariform perforation plates.

Senf- (Sinapis alba L.) und Zuckerrübenpflanzen wurden in der Phase des ersten echten Blattpaares mit dem Herbizid Pyrazon (=1-Phenyl-4-amino-5-chlorpyridazon-6) in Form eines Spritzpulvers-Pyramin-in der Konzentration 0,4% besprüht. 1, 4, 7 und 14 Tage nach der Besprühung wurde mit Hilfe der volumetrischen Methode nachJermakov und Mitarbeitern die Katalase-Aktivität im Blattsaft gemessen. Es wurde festgestellt, dass die Katalase-Aktivität in den Blättern der sensitiven Pflanze (Senf) durch die Einwirkung von Pyrazon im Vergleich mit dem Blattsaft aus unbesprühten Blättern herabgesetzt erschien, wogegen sie in den Blättern der resistenten Pflanze (Zuckerrübe) nicht abgesunken war.

The unicellular algaeScenedesmus obliquus (125),Chlorella pyrenoidosa (82) andCoccomyxa solorinae saccatae (111) were studied with respect to the form of uptake of potassium, phosphate, calcium and zinc ions and to the energy sources involved: light under autotrophic conditions, glucose under mixotrophic or heterotrophic conditions (in light and in darkness or together with yeast extract as an auxotrophic substrate). We respected the trophic conditions of algae when preparing the experimental material (precultivation). The following conditions were reached:
(1) The three algae grow faster in a glucose medium under mixotrophic conditions and are capable of growing on it also heterotrophically:Ch. pyrenoidosa andSc. obliquus grow substantially better thanC. solorinae saccatae. The first two algae grow more intensively in a glucose medium containing yeast extract whileCoccomyxa does not. After cultivation under mixotrophic conditions the first two diminish endogenous respiration, the third raises it. Glucose stimulates respiration in the first two when grown autotrophically, while after mixotrophic cultivation the effect of glucose is suppressed inCh. pyrenoidosa and in the other two only after growth on glucose with yeast extract.
(2) A relationship between sorption and metabolism was established for potassium in all the algae investigated. The effect of light is generally positive, heterotrophic components (glucose and possibly yeast extract) stimulate the uptake in the dark as long as they represent a suitable mixotrophic medium for the given alga.
(3) The uptake of K⁺ was proportional to concentration in solution and independent of Ca²⁺.
(4) The uptake of phosphate is clearly stimulated by light, while no stimulation under mixotrophix or heterotrophic conditions on glucose was observed-actually, a depression usually took place.
(5) At concentrations from 10^-6M to 10^-2M the uptake of phosphate is non-linearly but positively related to the concentration in the medium. The presence of Ca²⁺ is the cause of non-metabolic forms of phosphate sorption.
(6) Two forms of calcium uptake were found: the predominant one is adsorption which can be associated with the presence of phosphate ions; the metabolic uptake represents a considerably lower fraction which is characterized either by a light dependence or at least by a rise of calcium content between t=0.1-6 h.
(7) The absorbed Ca²⁺ can be washed out up to 75% with dilute hydrochloric acid. The total adsorption and remainder after washing depend on the pH of the solution from which the sorption took place (a considerable rise beyond pH 6.5). A substantial effect on the formation of the adsorption system was found to be due to organic nutrients. Algae after mixotrophic precultivation possess a decreased sorptive capacity.

The described virus of cow-parsnip,Heracleum sphondylium L., was found in three ruderal localities of Greater Praha. The symptoms are manifested by decolorations which consist of bright yellow areas spreading from the centre of the leaf blade along the main veins. These symptoms appear severely in May. Under higher temperatures and in a chronic stage of infection the symptoms are more or less masked. The disease is mechanically transmissible to parsley, coriander, parsnip, dill, sowbane,Chenopodium quinoa and C.giganteum. The author failed to transmit the disease to celery, carrot, caraway and to 27 species of differential host plants, he failed in the transmission of the virus by the dodder,Cuscuta campestris YUNCK., too. Thermal inactivation point of the virus lies between 51° and 55° C. Infectivity of extracted sap was lost after 2 days at room temperature.

If both cotyledons are amputated from non-decapitated pea seedlings, the intensity of transport of³²P into intact epicotyls is raised more than twofold. This is apparently connected with the regulatory-inhibitory effect of the cotyledons that can be simulated by a 0.1% paste of indoleacetic acid (IAA). If both amputated cotyledons are replaced by this paste, the intensity of³²P transport is again decreased to the level found in plants with intact cotyledons.
When etiolated pea seedlings grown in the dark in 100% relative humidity were decapitated, the³²P transport to the top of the epicotyl stumps covered with 0.5% IAA paste was strikingly decreased if the stumps were covered below with a 10% paste containing chlorocholine chloride (CCC) or with a 0.5% paste containing triiodobenzoic acid (TIBA). On the other hand, the intensity of³²P transport was significantly increased if the IAA paste was put above a 0.5% paste with kinetin which alone does not raise the transport intensity. No such synergism toward³²P transport could be established between IAA and gibberellin.

The changes of stomatal and cuticular transpiration of bean plants were investigated by graphical transpiration curves method (Slavík 1958). Bean leaves were infected by fungusUromyces appendiculatus (Pers.) Link. After the infection the intensity of stomatal transpiration had a decreasing tendency. Beginning with the sixth day after infection, the proportion of stomatal and cuticular transpirations becomes more expressive, i.e. the leaves transpire more by cuticles than by stomata. The higher share of cuticular transpiration brings extensive water relations to the diseased plants.

In der Arbeit wurde der Einfluss der Vorkulturen von Lein, Korn, Mohn und Ackersenf auf die folgenden Kulturen der gleichen oder einer anderen Art bei unmittelbar aufeinanderfolgenden Aussaaten sowie bei Aussaaten nach verschieden langen Intervallen unter Abstufung der Dauer der Lagerung des Bodensubstrates untersucht. Die Versuche wurden in Gefässen mit Komposterde durchgeführt, die im Versuchsgarten aufgestellt worden waren. Es wurde das Wachstum der Erst- und der Folgekultur mit Hilfe der Bestimmung der Trockensubstanz der oberirdischen Teile und der Wurzeln gewertet. Im Laufe der Wachstumsentwicklung der Folgepflanzen wurden Bodenproben entnommen und in denselben der Gehalt an physiologisch zugänglichen Stickstoff-, Phosphor- und Kali-Mengen bestimmt.
Alle vier in Betracht gezogenen Vorpflanzen bewirkten nachweisbare Veränderungen des Wachstums der Folgepflanzen. Lein und Mohn wirkten auf lein und Zuckerrübe als Folgepflanzen durch autopathische oder allelopathische Faktoren im Boden. Die Wirksamkeit von Korn als Vorpflanze auf Korn und Ackersenf als Vorpflanzen auf Gerste war nicht so deutlich. Von den Ergebnissen der beiden letzten Fälle lässt sich nicht direkt auf das Vorhandensein autopathischer oder allelopathischer Faktoren schliessen.
Bei unmittelbarer Kultivierung von Folgepflanzen im Boden der Vorpflanzen ohne Lagerung wurden nur Wachstumshemmungen festgestellt. Versuche mit abgestufter Lagerungsdauer bieten die Möglichkeit eine ganze Skala von Wachstumsänderungen an den Folgepflanzen von der Hemmung bis zur Stimulierung zu erfassen. Die Wirksamkeit der Vorpflanze auf die Folgepflanze ändert sich erheblich mit der Lagerungsdauer des Bodens nach der Vorpflanze.
Die Wachstumsänderungen der Folgepflanzen ergaben mit Ausnahme der Versuche mit Korn und teilweise mit Ackersenf weder Beziehungen zu den Veränderungen des Gehalts der untersuchten Nährstoffe, noch auch zur angewachsenen Pflanzenmenge der Vorkultur.

In den Ksimwurzeln eines Kultivars vonPhaseolus vulgaris nanus sind in der Wurzelspitze die Zellen in Päckchen von meist vier oder acht Zellen, die von einer gemeinsamen Zelle abstammen, angeordnet und gut voneinander zu unterscheiden. Diese Anordnung bestätigt den Befund von WAGNER (1937), dass jede Zelle des Wurzelmeristems vom Augenblick ihrer Entstehung an nur eine geringe Anzahl von Teilungen durcl.macht, da die Zellgruppen höchstens aus aeht oder neun, meistens aber aus vier Zellen bestehen. Ausserdem sind diese Zellgruppen in ziemlich gut unterscheidbaren Querscheiben angeoidnet, so dass es scheint, dass die Erstlingszellen jeder Querscheibe rbytmisch, allerdings nicht absolut gleichzeitig, gebildet werden. Obzwar es scheint, dass die Mitosen in der Wurzelspitze unregelmässig verteilt sind, ist es doch nicht der Fall. Das Wachstum der Zellen sowie ihre Teilung gehen rhytmisch vor sich.