1912] PACE— PARNASSIA 309 



figures show that often two of the megaspores begin to develop, 

 apparently either two of the lower three, second and fourth (figs. 

 16-18), second and third (fig. 17), third and fourth (figs. 22 and 24). 

 In fig. 25 one of the two upper adjacent megaspores and the fourth 

 one began to develop, but the upper one is in the best condition, 

 the fourth one being less dark than the other two, but darker than the 

 upper one. The epidermis is quite pale over this spore. Fig. 23 

 has the appearance of five megaspores, but one nucleus is quite 

 small with apparently only one chromosome, and is probably the 

 result of an abnormal division like that shown in fig. 12. 



The epidermal layer of the nucellus begins very early to dis- 

 integrate. These cells nowhere had the usual appearance of 

 disintegrating cells. As is well known, cells disintegrating under 

 apparently similar conditions stain deeply and have a more or less 

 crushed or squeezed appearance. But here they seem to grow paler, 

 as if the cytoplasm within them were diminishing, and finally all 

 contents disappear. Later the walls also are more or less com- 

 pletely absorbed. An attempt to show this is made in figs. 24, 26, 

 27. In fig. 24 the whole epidermal layer is pale almost to the base 

 of the fourth megaspore; in figs. 26 and 27 the cells are disappearing 

 from the upper part of the nucellus, leaving the megaspores lying 

 next to the inner integument. The disintegration in this region 

 continues until only the lower end of the sac is inclosed by nucellar 

 tissue, the greater part of it being in contact with the integument 

 and having no cells between it and the micropyle (figs. 30, 31, 

 33~36). Chodat's (3) figs. 661-666 show this disintegration of 

 nucellar tissue. He says: 



Chez beaucoup de Gamopetales et ches quelques Dialypetales la megaspore 

 qui s'est developpee dans un tres petit micelle dissont le sommet de celui-ci et 

 fait saillie an dehors dans le micropyle. 



The disorganization of this layer of cells may furnish food to the 

 upper megaspores and thus give them a better chance to develop 

 than they would otherwise have. On the other hand, it is altogether 

 possible that this disintegration is due to the unusual activity of 

 these 



megaspores 



Fig. 27 shows a two-nucleate sac that developed from the second 

 megaspore ; the third megaspore is quite large and as yet shows no 



