82 McKenney — Observations on the Development 



fundament. Following the formation of the secundine funda- 

 ment the primary tapetal cell usually divides by a penclinal 

 wall into two cells. By these successive divisions, the arche- 

 sporium becomes pushed down into the tissue of the nucellus, 

 so that, instead of lying just beneath the epidermis, it is 

 separated from it by a chain of three cells (Plate XI, Fig. 3). 



The archesporium now passes through a growth period of 

 considerable duration. After the growth phase, the arche- 

 sporial nucleus divides and the archesporium becomes divided 

 by a periclinal wall into two equal-sized daughter cells. 

 (Fig. 4). I have only been able to observe this division in 

 the anaphase and telophase stages. The anaphase stages 

 observed, however, were quite clear and the number of chro- 

 mosomes could be readily counted. The number of chromo- 

 somes, which in this division enters into the formation of the 

 daughter nuclei, is eight (Fig. 4 a). All the divisions of the 

 surrounding nucellar cells and the first division of the arche- 

 sporium show sixteen chromosomes. Hence it seems quite 

 probable that this last division of the archesporium is the 

 reduction division. 



Of the five cells formed by the division of the primitive 

 archesporium, the three outer remain inactive while the two 

 inner grow actively until they become two to three times as 

 large as the outer three. Attendant on this great growth of 

 these daughter cells of the archesporium, is a gradual degen- 

 eration of some of the neighboring nucellar cells. The outer 

 of these two daughter archesporial cells is the young embryo- 

 sac cell. The nucleus of each of these cells divides, but no 

 cell wall is laid down between the daughter nuclei. Thus two 

 bi-nucleate cells are produced (Fig. 5). The inner bi-nucleate 

 cell becomes passive for a time. The outer bi-nucleate 

 (embryo-sac) cell, however, elongates until it becomes about 

 twice its former length. The bi-nucleate cells again become 

 active and by the division of each nucleus two quadri-nucleate 

 cells are produced, the nuclei of the outer bi-nucleate cell 



