We have been studying the genetic effects of X-ray irradiation on the silkworm, Bombyx mori, since 1927. In the present paper is described one of the obtained results. The larval marking genes S(=PS, striped), P (normal), and p (plain) are multiple allelomorphs situating on the same locus of the second chromosome, and are linked with the blood colour gene Y (yellow) and y (white). The standard crossing over value between S and Y in the heterozygous male is known to be 25.6%. Several male moths from a Chinese SY strain were treated with X-rays, and then mated by Py females from a Japanese race. In F1 we got 15 mosaics among 2907 individuals, and one of the mosaic females was mated to a Py male of the same strain as used in the P-generation crossing. The offspring of this mating continued to show very peculiar modes of segregation: 1) Complete repulsion of P and Y in both sexes instead of partial linkage in the male side in the normal occasion; 2) when Y and y segregate in the present strain, Y always shows deficit to the expectation. The peculiarities mentioned above may be accounted for as follows. In the F1 S-P mosaic, S mutated to p in a number of somatic as well as germinal cells which gave rise to pYPy offspring, hence repulsion between P and Y! The mutated pY chromosome is represented as pY. No crossing over occurs, in either sex, between pY and Py chromosomes, perhaps in virtue of inversion which supposedly took place in pY chromosome. The pY chromosome behaves as a partial lethal which chiefly acts in the postembryonal life, thus the shortage of Y individuals is resulted, the counts being made only in full-grown larvae. The lethal action of pY is of course strongest in the homozygote, but it does not lose the lethal action even in the heterozygous state, i.e. it behaves as a partial dominant lethal.
The object of this paper is to present new evidences of the linkage relation between the genes for the form of leaves and the number of seeds per pod of soybeans. The varieties used are“Wearucong”and “Yanta”, the former having broad leaves and two-seeded pods and the latter narrow leaves and three-seeded pods. The results obtained in crossing experiments on the characteristics concerned are summarized as follows: 1. The narrow leaf (r) is a simple recessive to the broad leaf (R) and in F2 the ratio of the latter to the former is about 3:1. This relation holds true for the two characteristics with regard to the number of seeds per pod, i. e., the two-seeded (F) is dominant over the three-seeded (f), segregating in F2 in an average ratio 3:1. 2. There is a linkage relation between R and F, the crossing over value being about 10 per cent. 3. The action of the gene for leaf form interferes to some extent with the action of the gene for seed number per pod, and a number of genes other than the leaf form gene seem also to interfere with the action of the gene for seed number per pod.
1. In this paper which is the first report of the studies on the chromosome numbers in alpine-plants, the numbers of chromosomes obtained in 28 species of Japanese alpine-plants have been described and compared with those of non-alpine-plants of the same or related genera in order to get evidence as to the relation of ecological conditions to the number of chromosomes. 2. The results of the investigation is shown in Table 1. Coefficient of x means multiple of the corresponding basic chromosome number (x) already known in the related group. The numbers given in column 2n of the table are the somatic numbers of chromosomes counted in the root-tips of almost all of the plants studied. 3. A few genera in which no chromosome number has as yet been known, as far as the writer is aware, are described as multiples of the presumed basic number. These are put in parentheses in the table. 4. Among the alpine-plants studied, some have proved to be diploid, but the others such as Potentilla nivea L. var. asiatica Nakai, Astragalussecundus DC. and Pentstemon frutescens LAMB. have been found to be extremely highly polyploid.
1. The haploid numbers of chromosomes in a number of species and garden varieties of Capsicum, Solanum, Physalis, and other genera in Solanaceae were determined. 2. 49 garden varieties in Capsicum annuum, 37 such in Solanum Melongena, 6 other species in Solanum, 3 species in Physalis and 2 species in Datura were observed to present 12 chromosomes in haploid. Different numbers were also observed in some other plants studied. 3. A form of Physalis pubescenswing n=24 was found, and it was recognized, from its chromosome configulations in the meiosis, to be an autotetraploid.