Flllk : CONTIUBUTIONT TO THE LIFE-HISTORY OF RU.MKX. 141 



Figs. 8 and 9). The cavity of the macrospore, which I shall 

 now designate by the usual name of embryo sac, continues 

 to increase in size as it approaches the condition shown in Fig. 

 II by the continual absorption and pressure upon surrounding 

 cells. The relative position of cytoplasm and vacuoles in Fig. 9 

 is hardly normal, the nucleus of the macrospore more com- 

 monly lying along the central longitudinal axis of the spore. 

 In another preparation showing the dividing nucleus of the mac- 

 rospore, the nucleus was in this more usual position, and no 

 vacuole was seen. Fig. 11 show^s the two nuclei derived from 

 the nucleus of the macrospore and two tapetals and two other 

 sporangial cells nearly absorbed. Of these two nuclei it is 

 quite common to find the lower one larger, probably as a result 

 of better nourishment, and, apparently consequently giving rise 

 in division to a larger number of chromosomes. 



The condition as to chromosomes could not be studied, but I 

 noticed relative sizes carefully. As instances of difference in 

 size of the two nuclei, the researches of Sargant,* Mottierj and 

 .GuignardJ may be cited. I examined a number of the embryo 

 sacs showing the two nuclei, and it would seem that the lower 

 nucleus becomes very slightly larger than the upper (Figs. 11 

 and 12) . The slight difference may not be constant, and indeed 

 in the closely related Polygomun divai'icattim Strasburger§ shows 

 the upper nucleus larger than the lower. This stage of develop- 

 ment was quite frequently observed, but the next, in which two 

 nuclei appear in each end of the sac, was only seen twice (Figs. 

 13 and 14) . The first of the two figures shows the probable posi- 

 tion of the two nuclei during division as a persistent spindle was 

 seen between the anterior pair. Then the anterior pair seems 

 to result from the division of a nucleus lying transversely in the 

 anterior end of the sac and the posterior pair from a posterior 

 nucleus lying longitudinally in, the sac. This position of the 

 two nuclei while dividing is the common one in plants so far as 

 I can ascertain. Fig. 14 represents a later stage, in w^iich the 



*Sargant, Ethel. The Formation of the Sexual Nuclei in Lilitini martagoti. 

 I. Oogenesis. Annals of Bot. 10: 464. S. 1896. 



tMottier, David M. Ueber das Verhalten der Kerne bei der Entwicklung des 

 Embryosack und die Vorgange bei der Befruchtung. Jahrbiicher fiir wissen- 

 schaftliche Botanik 31 : 132. 1897. 



tGuignard, L. Nouvelles Etudes sur le Fecundation. Ann. des Sci. naturelles 

 Botanique VII. 14: 1S7. 1S91. 



§Strasburger, E. 1. c. Fig. 15. 



