Beta-ray irradiation effects on structural changes of the chromosomes in root tip of rye, Secale cereale L., seedlings, particularly the frequency of chromosome bridge induction at anaphase stage treated with radioactive sulfur (S35) solutions were studied in this experiment. Among the four different concentrations of isotope solution, the lowest one, 0.4$\mu$c solution, has shown weak effect on the induction of chromosome aberration. On the other hand, higher concentration, 25.6$\mu$c solution, induced higher frequency of chromosome bridge induction as much as 4.3%. Concerning the relationship between the ages of after treatment and the ranges of concentration, the higher concentrations showed more pronounced effects than the lower ones.

The effect of radioactive sulfur-35 on the growth and tissue respiration in rye, Secale cereale L., seedlings were studied in this investigation. The growth and respiration rate of the materials treated with the different intensities of radioactivity, represented by the different concentration(${\mu}c$) of radioactive sulfur were shown similar effects in treated groups as those of Gamma-ray or X-ray irradiation on plant materials. However, in the groups of ($0.1{\mu}c$ and ($0.4{\mu}c$ S35-solution, the growth and respiration rate were stimulated somewhat more clearly than in case of control. And the higher concentration groups, $1.6{\mu}c$, $6.4{\mu}c$, and $25.6{\mu}c$ were depressed of the growth and tissue respiration rate. The present data could be explained on the basis that the higher concentration treatments with the radioactive isotope did produce injury to the plant metabolism generally, but the moderate treatment would stimulate to the plant growth and tissue respiration.

Since Taquet's first discovery of wild P. yedoensis at Mt. Halla, Korea, in 1908, its morphological chracteristics and question of origin of cultivated yedoensis have given controversies to the botanists. Takenaka, through his experiments on the hybridity of cultivated P. yedoensis, recently holds the opinion that P. yedoensis might have originated in Izu peninsula, Japan. The author presents the summarized report on the wild P. yedoensis and its putative parents based on his 2 years' investigated carried out at Mt. Halla during his breeding experiment of genus Prunus. The species of cherry tree used in the present investigation were identified by Prof. Mankyu Park and Mr. Jonghyu Pu, Korean taxonomists. 1) Wild cherry trees which grow wild in Mt. Halla and whose blooming season is April are mostly P. subhirtella var. pendula form. ascendens and P. donarium P. yedoensis is rare in number, around 10 individuals, having been found in a half century. 2) Individuals of wild yedoensis are variable in some of their morphological characteristics. This is, also, true in other species of Prunus. 3) Wild yedoensis whose vigorous growth, sterility, and rarity in number suggest hybrid origin, has intermediate characteristics between the P. subhirtella and P. donarium. 4) Due to the abnormal weather of the island and various environmental factors such as havbitats, some of the early-blooming subhirtella and late-blooming donarium would bloom at the same time, giving these two species the changes to cross. 5) Wild yedoensis is slightly different in some of its quantitative characters from cultivated species.

Interaction occuring among the different Ca concentrations, pH and temperatures in the promotive effect of Ca in pollen growth was studied by using pollen from Crinum asiaticum and Cryptostegia grandiflora. Data for pollen tube elongation were found to be more indicative of representing the promotive action of Ca ion in pollen growth than those for pollen germination, and were served to evaluate the experimental results. The pollen growth increased as the concentration of Ca increase. The optimal pH range for pollen growth shifted from the lower pH to the higher as the concentration of Ca increase. The characteristic Ca effect was disappeared, and no pH effect at various ranges was observed when pollen grains were grown at the low temperature(8$^{\circ}C$). The Ca effect became quite pronounced if temperature were raised. The Ca effect became even mroe striking if the condition was in higher pH ranges (weak alkaline). Higher pH ranges were found to be more favorable for the Ca action, whereas higher temperature was required to bring about more pronounced Ca effect. Thus, the longest pollen tube was obtained with the highest pH, temperature adopted for the medium supplemented with Ca in the present experiment, and the shortest tube with the lowest temperature applied at the highest pH. Pectin synthesis in pollen tube was considered as a metabolic process, whereas Ca binding in pectin of the pollen tube wall as non-metabolic in nature. Disappearance of Ca effect at the low temperature was probably brought about by blocking the metabolic synthesis of pectin, and nonmetabolic Ca binding seems to take place more extensively with higher concentrations of Ca and at higher pH levels than the lower.