16 Miyake, The developmeut of the gametophytes etc. 



In the conjugating nuclei of Jimipcrus communis Noren 

 (1907) observed the decrease of the chromatic substance and the 

 corresponding- increase of the micleolus-like bodies the "Pseudo- 

 nuclei" which he thinks contribute the greater part of the substance 

 of the chromosomes. x4.1though I do not have enough evidence to 

 speak for or against Noren's view, some of my preparations like 

 fig. 90 may suggest the possibility of such a process. In figs. 92 

 and 114 are shown completely formed spindle, with chromosomes 

 accumulating near the equator of the former; the paternal and 

 maternal Clements can no longer be distinguished. 



The result of the first division is shown m fig. 94; two 

 daughter-nuclei are surrounded by dense mass of starch-granules, 

 and they travel toward the base of the Q^g. As they reach the 

 base of the archegonium (figs. 95, 96), both nuclei divide simul- 

 taneously, and four free nuclei are formed as shown in fig. 97. 

 The third division which now follows is also simultaneous and 

 results in the formation of eight nuclei, which are arranged in 

 tiers as shown in fig. 98. Walls are then formed between the 

 nuclei, the upper tier remaining open at the top. 



In Cryptomeria, Lawson (1904b) finds that the continuous 

 fibrils of the spindle persists, and the first cell-membranes of the 

 embryo are formed between the nuclei. According to Miss Fer- 

 guson (1901, 1904), who has studied the first waU-formation of 

 the proembryo in Piniis, the spindle fibers of the third division 

 seem to disappear before the walls are formed between the nuclei. 

 Although I have not followed the process of the first wall-formation 

 in detail, I am inclined to accept the view of the latter investigator 

 on this point. The stage as shown in fig. 98, in which no trace 

 of spindle fibers is visible between the eight free nuclei, can hardly 

 be interpretted in accordance with Lawson's view. 



While in the Äbiethieae, the eight nuclei of the proembryo, 

 as a rule, arrange themselves in two tiers of four nuclei each, the 

 same stage of Ownninglmmia, Cryptomeria and Taxodium does not 

 show such regularity in the arrangenient of the nuclei. Coker 

 (1903) States that in Taxodium two nuclei are situated at the base, 

 and six nuclei lie above them in oue plane. He adds: "while this 

 is the usual arrangement, it is not uncommon to find only one at 

 the base, while the other seven are arranged above it. In a few 

 cases there were three below and five above." In Cumämjhamia 

 the number of cells in each of the two tiers is also not constant; 

 it seems, however, that the upper tier generally contains five nuclei 

 and the lower three, as shown in fig. 98. It was sometimes found 

 that there are two below and six above. The other combinations 

 of cell-arrangement are also possible. The lower group of com- 

 pletely-walled cells may not lie in the same plane; they are some- 

 times found one above the other instead of side by side. 



The nuclei of the upper tier then divide simultaneously and 

 the walls are formed between the daughter-nuclei (figs. 99 — 102). 

 We have now in the proembryo two tiers of cells and one tier of 

 the incompletely-walled cells (figs. 101, 102). Lawson (1904b) 



