1) Morphology and fertility of about 100 individuals were investigated with special reference to the relation between the fertility and the morphology, or the meiotic behaviors. 2) The external morphology is quite divergent, but the general appearance of the F4 population is said to be Paraixeris-type. 3) There are no definite relations between the external morphology and the ertility. 4) The correlation between the pollen fertility and the rate of achene setting is small (r=0.20). The low fertility of the pollen is correlated with the multivalents and the low rate of achene setting with the prematurely separating bivalents. 5) The fertility was much restored in F4 in spite of an increase of meiotic irregularities.
The authors have observed the chromosome numbers of Mexican Tea (Chenopodiumambrosioides L.) and American Wormseed (Chenopodium ambrosioides L. var. anthelminticum A. Gray), together with some other species of Chenopodium. Results obtained are summarized as follows: 1. The authors have determined for the first time that, the chromosome numbers of Mexican Tea are n=8, 16, and 24, and that of American Wormseed is n=32. 2. It has been shown for the first time that the basic number of Mexican Tea and American Wormseed is 8. 3. Diploid (n=8), tetraploid (n=16) and hexaploid (n=24) plants of Mexican Tea, and American Wormseed (n=32) have morphologically each different characteristic features. 4. Chromosome numbers of some other species of Chenopodium observed by the authors are shown in Table 2, and it has been shown for the first time that their basic number is 8.
1. The author investigated the pollen tube growth in interspecific pollinations of the genus Cucurbita, with the intention of confirming the relations between the pollen tube growth and cross-compatibility. 2. The size of floral parts in female flowers varies according to species and varieties. For the comparison of the pollen tube growth it was measured respectively (Table 1). 3. The time for pollen tubes to make its way from stigmas to ovaries is as follows: In C. pepo var. Delicata it takes three hours to reach the ovaries, while in C. moschata vars. Futtsu Kurokawa and Aizu Gokuwase it requires four hours and in C. maxima var. Delicious five hours. 4. As seen from the degree of the pollen tube growth, the Cucurbita crosses can be classified into the following three combinations: (a) The first case of combinations where pollen tubes are able to grow deeply into ovaries, reaching the end of main conducting tissues; C. maxima×C. moschata (Fig. 3), C. moschata×C. maxima (Fig. 6), C. maxima×C. pepo (Fig. 4). (b) The second case of combinations where the pollen tube growth is delayed within the ovaries; C. moschata×C. pepo (Fig. 7). (c) The third case of combinations where the pollen tube growth is inhibited at the upper regions of ovaries; C. pepo×C. maxima (Fig. 9), C. pepo×C. moschata (Figs. 10, 11). 5. From the results mentioned above and the percentages of fruit set obtained by the present author and other investigators, it may be said that crossings between C. maxima and C. moschata are of imperfect compatibility (Tables 2, 3). 6. The proper time for measuring the pollen tube growth may be 27-30 hours after the pollinations. 7. The peculiarity of C. pepo as staminate as well as pistillate parents was discussed.
The fertile F1 plant (TcSF1-1) T. compactum (n=21)×S. cereale (n=7) and its offsprings were studied genetically and cytologically with the purpose of breeding the constant type in the descendants. The number of somatic chromosomes of this F1 is 28, the sum of the gametic numbers of chromosomes of the parents. The external characters of the F1 resembled more closely to T. compactum than being intermediate between the parents. The maturation division in PMC-s of the F1 may be classified into two types A and B. A-type gives rise to the pollen grains having the number of chromosomes 28/2 or nearly so, and B-type results in the pollen grains with the number of chromosomes 2n or approximately so. In B-type non-conjugation and the formation of restitution nucleus were observed. The pollen grains having 2n chromosomes, produced through the course of non-conjugation and restitution nucleus are provided with A B D genoms from T. compactum and R genom from S. cereale. These pollen grains play an important role in the formation of amphidiploid. The number of somatic chromosomes of F2 plants were 47, 48, 54, 55, 56 and 58. In the F2 generations hypo and hyper amphidiploid plants resulted from the abnormality in the maturation division of F1 were frequently found besides the amphidiploids with 56 chromosomes.