The dispersal mechanism of Japanese yew (Taxus cuspidata S. and Z.) seeds by animals, especially birds, was studied in the Tomakomai Experimental Forest of Hokkaido University in southern Hokkaido. Two sample trees ( I and II) were investigated for seed production and their consumption by animals. Trees I and II produced 36, 628 and 2, 785 seeds, respectively. The greater part of these seeds were consumed by birds (I: 73%, II: 46%) and rodents (I: 14%, II: 34%). About 5% of all the seeds, however, were scatter-hoarded by the varied tit (Parus varius T. and S.) which stored 37% of them in bark fissures and among the needles of coniferous trees and 63% of them on the ground. The seeds on the ground were put on particular sites such as around the roots of trees and on steep and bare slopes. These caches were related to the distribution of yew seedlings. Moreover, the frequency of dispersed seeds plotted against distance was related closely with the density of the seedlings. From these results, the scatter-hoarding of seeds by the varied tit was suggested to be important in the dispersion of yew. The relationship between yew and the dispersal agents, including not only the varied tit but other animals, also is discussed.

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In this paper, the author considers that tapering grades are the same among the trees whose actual stem-curves are similar, and he proposes to define a tapering grade as the decreasing grade of diameter on a kind of relative stem-curve obtained by reducing an actual stem-curve in both diameter and height directions on a scale of one to tree-height. This relative stem-curve can be disassembled into the normal, relative stem-curve and the corresponding slenderness-ratio, and is given as the quotient of the former to the latter. The changes of tapering grades in even-aged stands of Cryptomeria japonica D. DON, Chamaecyparis obtusa S. and Z., Pinus densiflora S. and Z., and Larix leptolepis GORD, were investigated by using measurements of many felled trees. The results were: 1) The tapering grade decreased largely in the lower part of the stem until a certain age, whereas the change of tapering grade with age was compara-tively small in the upper part of the stem. 2) The greater were the density-control levels, the smaller were the tapering grades. 3) The differences of tapering grades among density-control levels for C. japonica were larger than those among tree species. 4) The vertical changes of tapering grades showed different patterns among tree species. Judging from these results, it is concluded that the new definition and expression of tapering grade proposed here is effective for practical use.

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The CO₂ evolution rate was investigated in clarifying the characteristics of microbial activity accompaning the decomposed of living sugi (Cryptomeria japonica D. DON) needles dropped to the forest floor. CO₂ evolution rates of needles in different stage of decomposition increased significantly with increasing temperatures and needles water-contents. Characteristics of the CO₂ evolution rates with needles water-contents differed between red-brown, grey-brown and brown needles. Decomposition of brown and grey-brown needles had about the same environmental dependence judging from the determined relationships between temperatures, water contents and CO₂ evolution rates, because these two color classes had nearly the same regression curves of the CO₂ evolution rates. Characteristics of the CO₂ evolution rates apparently were different between the fraction of the large water absorption capacity of brown needles and that of the small water absorption capacity of red-brown needles.

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The buds of Tilia amurensis RUPR. seedlings were cultured on the modified MURASHIGE and SKOOG (MS) and SAITO and IDE (IS) media to establish an effective micropropagation method. To investigate the effect of 6-benzylaminopurine (BAP) on shoot development in bud culture, five levels (0, 0.5, 1.0, 2.0, and 5.0mg/l) of BAP concentrations were tested. The best results were obtained with 1.0mg/l of BAP in both media. The grand mean of percentages of shoot development for the five levels of BAP in MS medium was somewhat greater than that of IS medium. Developed shoots were subcultured to induce multiple shoots on MS and IS media supplemented with 0.2mg/l of BAP. The growth of shoots and multiple shoots was stimulated more in explants that were cultured previously on media with 1.0mg/l of BAP. The maximum rate of multiplication per explant was six times after 30 days culture and the mean was 2.6 times. A 91.7% rooting rate from cultured shoots was achieved on a half-strength MS medium with 0.3mg/l of indole-3-butyric acid (IBA).

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Germination of the seeds of Guazuma crinita MART. and Guazuma ulmifolia LAM. was investigated, both at constant temperatures of 28°C, 23°C, 18°C, and 13°C, and at alternating tempera-tures, of 20°C and 10°C for 16h following 30°C and 20°C, respectively, for 8h. The germination percentage was greater at 28°C than at the other temperatures; in G. crinita it was about 50% after eight days and about 80% after 20 days in G. ulmifolia, but the germination percentage did not increase after that. When the seeds were heated in water at 60°C, the germination percentage at 28°C after 15 days increased by 33% in both species. Seeds heated in dry air at 40°C for 0.5 to 2h, responded favorable only in G. ulmifolia; the treatment for 2h was the best.

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