1). The maturation divisions of
Scirpus lacustris L. var.
typicus Honda f. pictus Honda (2n=39s+1S) and of
S. lacustris L. var.
Tabernacmontani Trautv. f.
zebrinus Makino (2n=42s) have been described. The first plant
pictus having one large compound chromosome in a somatic cell, has shown a sort of heteromorphic pairing in the first meiotic division as expected. The last form
zebrinus has shown rather regular meiosis.
2). In the 1-metaphase of
pictus a number of chromosomal configurations have been observed (cf. tables 1, 2); namely, in the first group (i) the compound chromosome S has conjugated with 3 small chromosomes (3s), giving a formula (1S+3s)+(15+n)
II+(6-2n)
I where n=0-3; in the second group (ii) S has conjugated with 2 small chromosomes (2s), giving a formula (1S+2s)+(15+n)
II+(7-2n)
I where n=0-3; (iii) in the third group, S has conjugated with only one Small chromosome (s), (1S+1s)+(14+n)
II+(10-2n)
I where n=0-4; (iv) in the fourth group, S has failed to conjugate with any small chromosomes, (1S+0)+(17+n)
II+(5-2n)
I where n=0-2; (v) in the fifth, several abnormal Gases were also observed. In Gase of
zebrinus, the first division being rather regular, the chromosome counts in the I-metaphase were made easily; 168 PMC's (84%) out of 200 observed were consisted of 21 bivalents.
3). The compound multivalents formed in the first division of
pictus have shown various mode of segregation in the I-anaphase. This hetermorphic pairs have segregated equationally as well as reductionally, according to the number of chiasmata between the compound chromosome and the univalents attached to it. Lagging chromosomes were observed now and then. The compound multivalents have always separated slowly. This is probably caused by the chiasma formation.
4). Chromosome counts in the II-metaphase were difficult. However, a few of them obtained have given some hints to the behaviour of the univalents and of the heteromorphic pairing. Judging from the tables 3 and 7, the univalents observed in
pietus may sometimes divide themselves in the I-metaphase, and sometimes pass to the poles at random as it is in fast.
5). In the II-anaphase of
pictus, remarkable structural hybridity, i.e. formation of chromatin bridges, occurrence of the lagging or precession chromosomes were observed. Chromatin bridges have been considered to have produced from the results of both crossing-over and unusual crossing-over between the compound chromosome and 1-3 small chromosomes attached to the formen. Generally, chromatin bridges have been formed in the first division and rarely in the second. But in the present Gase, the conditions were entirely reversed, i.e. they were not observed in the first division but only in the second.
6). In the II-telophase of
pictus, chromatin bridges were persistent. However laggards should have reached to the polen in time to he included, for the percentage of the cells containing laggards had decreased as the stage proceeds.
7). As a result of irregularities during the meiosis, there must arise various pollen grains containing variated chromosomal constitutions. Unfortunately, the pollen grain division was observed only in
zebrinus, where the chromosome numbers counted have varied 18 to 22.
8). Test of goodness of pollen grains of 3 types, i.e.
typicus (normal self-colored),
pictus (variegated form), and
zebrinus (variegated form), has shown 99.81% good for
typicus, 0% for
pictus, and 37.6% good for
zebrinus.
9). From the present karyological observations it has been shown that the large chromosome in
pictus is equivalent to 3 small chromosomes which were usually non-homologous to each other.
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