1) Effect of ethyl ether, ethylene, acetylene and carbon monoxide on the discharge of spermatozoid of Isoëtes from the microspore (male prothallium) was quantitatively investigated. 2) Ethyl ether which was found to be effective in Fujii's study in 1910, was found to be ineffective when it was carefully purified. 3) The positive effect of commercial ethyl ether on the phenomena was attributed to its volatile impurity and Fujii's conclusion (1925) that active substances are unsaturated compounds was confirmed. 4) The threshold values in the effect of ethylene, acetylene and carbon monoxide were determined.
By the application of Kamiya's dynamoplasmometry, the author found the following results concerning the motive force of protoplasmic streaming in the plasmodium, Physarum polycephalum. 1. There was no direct relation between the magnitude of the motive force and the weight of the plasmodium within certain limits. 2. After the plasmodium in one or both sides of the compartments was cut off, or after two plasmodia in the same compartment were fused together, the magnitude and the wave-form of the dynamoplasmogram changed considerably. In these cases, the above conclusion was also supported. 3. When the chloroform vapour was applied to both sides of the compartments, the magnitude of the motive force increased in low concentrations and decreased in high concentrations. In the latter case, changes in the wave-form of the dynamoplasmogram were observed. 4. When these vapours were applied to only one compartment, protoplasm showed a tendency to move into the non-treatment compartment, as indicated by the shifting of the wave upwards. In this treatment, the plasmodium develops a “tolerance” for the vapour in the case of low concentration.
The rate of growth of the pollen tubes is the same in self- and cross-matings with C. olitorius as _??_. The rate of growth of the pollen tubes is the same on self- and cross-matings with C. capsularis as _??_. There is a slight difference between the reciprocal matings. Germination is late in C. capsularis but the pollen tubes reach the base of the style ten minutes earlier. Incompatibility is not due to any retardation in the growth of the pollen tubes along the stylar tissue in either case. The shortness of the style between the species offers no advantage in overcoming inter-specific incompatibility.
Observations are presented on chromosomal aberrations in root-tip mitoses and microsporogenesis in plants grown from x-rayed dormant seeds of barley. The study was made as part of a considerable number of experiments over a period of five years. In all tests x-radiation was applied at 34 KVP and 27 ma. Dosages ranged from 0 to 32, 000 r. It was concluded that chromosomes in the resting embryo ordinarily responded to x-radiation as though they were monopartite, because induced breaks were almost always chromosomal breaks rather than chromatid breaks. This conclusion was based on: 1) the high frequency of paired, apparently identical dicentric chromosomal bridges and acentric fragments at anaphase in somatic cells of root tips; 2) the presence of unlike ends on some of these dicentric chromosomes; 3) the relatively rare occurrence of single bridges in these somatic anaphases. The rarity of single bridges at anaphase in somatic cells, in contrast with the frequency of paired bridges (even at low dosages), also was interpreted as indicating that the fusion of sister chromatids at a common breakage point, or following splitting of a chromosome during seed germination, did not often occur. Unlike ends on a dicentric chromosome also would not be expected if broken ends of sister strands fused. Usually two acentric chromatinic fragments do not join. Evidence for this is the fact that acentric fragments usually occurred in pairs (ranging in size from minute dots to rods as long as a normal chromosome) rather than as V's or rings as would be the case if their broken ends united. Thus, it seems that the centromere plays an important part in the union of broken ends of chromosome fragments. The observations suggest that acentric fragments are able to undergo one division, but do not persist beyond the subsequent resting stage. This opinion is based on the fact that these fragments usually occurred in pairs at somatic metaphase and anaphase, as though a piece of chromatin had reduplicated. If these fragments went into the telophase stage, returned to the condensed state and redivided again, quadruplet fragments should have been seen occasionally, but were not. However, it is true that most of the experimental observations were believed to have been made on the first cell division following radiation. At anaphase the acentric fragments were distributed freely in the cytoplasm, although they seemed to occur most frequently in the region of the equatorial plate. There was no evidence of any attraction between the fragments and the pole. Evidently a centric fragment attached itself as often to an acentric as to another centric fragment. This conclusion is based on the fact that there was a reasonably close parallelism between the frequencies of pairs of dicentric bridges in root tip cells (resulting from a union between two centric fragments) and interchanges in pollen mother cells (resulting from a union between a centric and an acentric fragment). If this relationship is proved to be true, it should be possible to predict fairly accurately the frequency of spikes with interchanges in their microsporocytes from the frequency of bridges in cells of root tips taken from seeds given the same x-ray treatment. Evidence is presented (see Discussion) which indicates that ordinarily, broken ends of chromosomes unite shortly after the breakage takes place. That is, most of the results were consistent with the theory that exchanges between irradiated chromosomes are usually the result of simultaneous breakage and fusion. However, a few observations seem to be accounted for most logically if it is assumed that delayed attachments between fragments occasionally do occur. Observations at meiosis in 3, 509 spikes revealed that the most common aberration was a ring-of-four (in 371 spikes), resulting from a simple reciprocal translocation.
1. It was pointed out that there are three types of irritability that have been stated to obey the well-known Weber law. These types, referred to as “animal type”, “vegetative type” and “intermediate type” of irritability, are characterized by the difference in the implications of the Weber law they follow, namely. ΔI/I=constant in the irritability of animal type, ΔQ/Q=constant in the irritability of vegetative type, ΔQ/I=constant in the irritability of intermediate type, where I is the strength and Q the quantity (or I×duration) of stimulus, and ΔI and ΔQ are their increment necessary to cause the response. The irritability of animal type and that of intermediate type are observed in various sensory responses of higher and lower animals, respectively, while the irritability of vegetative type is observed in various tropic movements in higher plants. The irritabilities of vegetative and intermediate type caused by a single stimulus share the property to obey the “law of the quantity of stimulus” which appears not to be applicable to the irritability of animal type, provided that the latter is observed with an ordinary time scale of experimentation. 2. In general terms, the following reversible reactions were assumed to occur in the physical system which primarily receives the action of the stimulus P_??_P' (i) P_??_P' (ii) of which only reaction (ii) is supposed to be induced by stimulus. The equilibrium of reaction (i) occurring independently of the effect of stimulus is assumed to be shifted appreciably towards the left-hand side of the equation. For this system, a parameter E corresponding to the “sensation” in the Fechner theory was assumed. The significance of this parameter is that its increment (ΔE) of a definite magnitude was made responsible to the occurrence of a definite response in organism, and that it is assumed to be related quantitatively to the free energy (F) of the system determined by the concentration of P' in the following manner: dE/dF=constant It was further assumed that the rate constants k, k' and ks of the above reactions are very large in higher animals, smaller in lower animals and extremely small in plants. 3. Based on these fundamental assumptions we could explain why different types of Weber law are met with in different organisms. The fact that the Weber ratio ceases to be constant at lower intensities of stimulus and becomes progressively larger with the decrease of the latter also received a satisfactory quantitative explanation by our theory. 4. By extension of the theory, the Weber law and the Weiss law could be united to a consolidated principle. In the light of the extended theory, the difference between the irritabilities shown by higher animals and plants is no more an absolute one, and it was shown that every living system can manifest either the animal type or vegetative type of irritability according as the relative length of the duration of stimulus applied. When the duration of stimulus is relatively suffi ciently short, we observe the “law of the quantity of stimulus” which is characteristic of the irritability of vegetative type. On the other hand, the “rheobase” observed when the duration of stimulus is relatively sufficiently long represents the duration-independent strength of stimulus necessary for response, which is characteristic of the irrita-bility of animal type. As to the “chronaxie”, it is nothing but the reciprocal of the rate constant (k') of the reaction P'→P assumed in our theory.