56 BOTANICAL GAZETTE [JANUARY 
- FORMATION OF THE MEGASPORE. ; 
Quite early in the development of the ovule an archesporial | 
cell (fig. 47) may be distinguished by its greater size and . 
greater avidity for stains. Its cytoplasm stains much more — 
Fic. 43. Nucellus with archesporial cell. K 1375. 
Fics. 44, 45. Same as fig. 43, but archesporial cell has divided, forming primary 
tapetal and primary sporogenous cells. X 1375. 
darkly than that of adjacent cells, while its nucleus takes 4 less 
intense stain. This cell enlarges rapidly and soon divides (jig: 
40), giving rise to the primary tapetal cell and the primary 
sporogenous cell (figs. 44, 45), this division usually occurring 
about when the carpel begins its rapid growth around the ovule 
(fig. 45). The primary tapetal cell may divide by a wall per 
pendicular to the one which separated it from the primary sporog = 
enous cell (fig. gz). I found no cases indicating that it divides — 
by periclinal walls to form a tapetal row. Later stages do not | 
show more than two layers of cells above the tip of the embry? 7 
sac, and since nothing was found which could be interpreted as 
remains of tapetal cells the conclusion that no later development 
occurs seems justified. The loss of differentiation in reaction ‘oe 
Se 
