The authors investigated the coastal vegetation at Nijigahama, Japan. It was studied there that the stratification by physiognomy was correct statistically, that the vegetation type was characterized by various coefficients, and that an objective standard whether any of sampling methods should be adopted or not was indicated by the intraclass correlation method.
1) In this report the morphological and cytological characteristics of Ixerisstolonifera (2n=16) and those of Ixeris japonica (2n=48) were compared. 2) The observations on the somatic chromosomes show that Ixeris stolonifera has two sets of chromosomes, each consisting of eight chromosomes, that Ixeris japonica has six sets of chromosomes, and that Ixeris japonica is regarded as an autohexaploid plant derived from I. stolonifera. 3) Several morphological characteristics of the hexaploid species are larger than those of the diploid species, and Ixeris japonica may be a gigas form of I. stolonifera. 4) The osmotic pressure of Ixeris japonica is higher than that of Ixeris stolonifera.
Nitrate, nitrite or ammonium salt was supplied toSpirodela polyrhizaandLemnavaldiviana which previously had been cultivated aseptically. They were placed partially in the light and darkness for an hour at 25°C, and then the consumed amounts of these nitrogen sources were measured. In some experiments leaves of Dahliawere also used. InSpirodela and Lemna the nirate reduction was not influenced by the light in some cases, but it was inhibited tolerably in the other cases. These differences seem to be related with the nutritional condition in the plant bodies. In Dahlia such effect of the light was more remarkable. The consumption of ammonia was accelerated clearly by the light in Lemna and Spirodela. In Dahlia either consumption of ammonia in a small amount was recognizable or it accumulated more than their initial content, so far as the present method permited floating leaves on the surface of the test solutions. The nitrite reduction was accelerated by the light. If the content of the nitrate in the plant bodies was large, this relation, however, did not clearly appear. The nitrate reduction was accelerated by the imhibition of the liquid in the plant bodies, or in the anaerobiontic condition in the nitrogen gas, but the Ammonium consumption was retarded by the same treatments. In the etiolated Lemna plants the nitrate reduction was weak and no influence of the light, but the effect of the imbibition and the anaerobiontic condition appeared. Form the facts mentioned above, it is considered that the effect of the light on the consumption of nitrate and ammonia seemed not to be direct. The light may be regarded to rather increases the partial pressure of oxygen in the tissues as the result of photosynthesis and this is able to be beneficial to the consumption of ammonia, but to act unfaborablly to the nitrate reduction.
Some attempts were made on the sweet potato leaf to see the quantitative relation between transpiration and stomatal opening. Transpiration from the upper surface of the leaf (Tu) was compared with that from the lower surface (Tl) by the cobalt paper method. The ratio (p) of Tu to Tl fluctuates from 0.49 to 1.0 in close relation to stomatal opening. When the stomata open widely, p may represent more nearly the ratio of stomatal transpiration of upper surface to lower as cuticular transpiration is lowered in this case. Provided that stomata of both surfaces behave equally, p should decrease as stomatal transpiration increases due to widening of the aperture. When further opening does not bring about so much increase in the transpiration as before, p may begin to increase inversely. Thus the stomatal aperture 4μ, which was observed at the minimum of p, seems to be the limit above which the change of stomatal aperture has less influence on the transpiration of the sweet potato leaf. When stomatal transpiration becomes extremely lowered, p may imcrease to approach 1. And it is found that 0.6μ is the limit below which the stomatal aperture have little effect on the transpiration. The above mentioned role of stomata in transpiration may hold good only when the water content is sufficient, for p appeared lower than to be expected when the leaf wilted in the afternoon.
The spiral structures of univalents and rod-shaped bivalents were studied in Tradescantia paludosa (n=6). In univalents the directions of spirals of the arms are independent across the kinetochore. The spiral structures of rod-shaped bivalent are somewhat different from that of the univalents. The directions of spirals in free arms distal to kinetochores are independent of each other, but arms forming a terminal chiasma are coiled in compensating directions.
1) 15-species of the mosses were investigated cytologically with special reference to the chromosome number and the heterochromosome. The results obtained are shown in Figures 1-34 and Table 1. 2) In every species studied by the present writer, it has been observed that the largest (H) and the smallest (h) chromosomes are the heterochromosomes, and the number of which was constant in the mosses belonging to the same genus. These facts correspond with what was described in the series 1 of the present paper and what Tatuno reported on many liverworts (1941) and some mosses (1951). 3) It is a remarkable fact that while Rhytidiadelphus calvescens has two sets of autosomes which are similar in shape to those of Rhy. triquetrus, both species have only one set of heterochromosomes consisting of H and h. Their karyotypes are as follows. Rhytidiadelphus triquetrus n=6=V(H)+2V+J+l+m(h) Rhy. calvescens n=10=V(H)+4V+2J+2l+m(h)