Fink: CONTRIBUTION TO THE LIFE-HISTORY OF RUMKX. 139 



led to the suspicion that the tapetum may sometimes fail to di- 

 vide. Fig. 5 shows four tapetal cells and the sporogenous cell 

 below somewhat more elongated than usual with its nucleus un- 

 usually near its upper end. That this elongated cell is the 

 mother cell of the macrospore instead of the macrospore itself 

 is proved by the outline of the inner seed coat, which shows its 

 early development as compared with its more advanced condi- 

 tion before the macrospore is produced (Fig. 10). Fig. 6 rep- 

 resents a single tapetum lying above a dividing mother cell, and 

 this may be the original tapetum which has failed to divide, 

 though a cell lying almost directly below it, and hence not 

 shown in the figure, may have been a second tapetal. Fig. 3 

 shows a typical mother cell apparently about ready to divide, 

 and showing two tapetals, neither of which would be likely to 

 divide again. 



After the formation of the protective cap of tapetal cells and 

 the enlargement of the mother cell of the macrospore, the latter 

 divides as usual, among the Archechlamydeae at least, into a row 

 of four potential macrospores. It is here that our subject proper 

 really opens since this mother cell, in which the reduction 

 of chromosomes takes place, stands between the sporophytic 

 and gametophytic generations, connected morphologically with 

 the former and physiologically with the latter. As the mother 

 cell divides the nucleus lies longitudinally at or a little above 

 the center of the cell (Fig. 6). As elsewhere in these studies, 

 the number of chromosomes could not be made out, but, in all 

 probability through failure to get a complete view of individual 

 chromosomes, there really seemed to be twenty-four in this nu- 

 cleus. The two cells resulting from this division were not seen, 

 but from the position of the dividing nucleus in several instances 

 observed, it may be assumed that the division is into two cells 

 of approximately equal size as observed by Strasburger* in Po- 

 lygonum divaricatum. This dividing nucleus of the mother 

 cell of the macrospore was about as large as that of the macro- 

 spore itself (Fig. 9) and, being like the latter a nucleus of a 

 large well-fed and consequently somewhat inactive cell, was ap- 

 parently a long time in dividing. The reduction of chromosomes 

 is supposed to be a process involving more time than is com- 

 monly occupied in mitotic division of nuclei ; and this process 

 doubtless also added further to the time occupied by this mother 



* Strasburger, E. Die Angiospermen und die Gymnospermen, p. 5, 1879. 



