498 BOTANICAL GAZETTE [JUNE 
The outline of the growing prothallus may remain smooth and 
even (fig. 36) or become very irregular (fig. 35). The irregularity © 
appears to be entirely due to two facts. The gametophyte, as 
already mentioned, is very delicate and plastic, and, in consequence, 
able to adapt its form to the cavity in which it grows. The second 
fact is that the cavity in which it is forming does not always enlarge 
regularly. Whether the irregularity is due in whole or in part to the 
action of the gametophyte is somewhat doubtful, as will be pointed 
out in the succeeding paragraphs. The development of the game- 
tophyte beyond the fertilization stage will be further described in 
connection with the maturity of the ovule and the organization of 
the seed. 
The cells surrounding the megaspore have already been men- 
tioned as being larger, having larger nuclei and denser contents 
than other nucellar cells. They perhaps correspond to the so-called 
spongy tissue. The character of these cells is shown in figs. 6-8. 
As the megaspore enlarges, the innermost layers of these cells die 
and lose their contents. ‘The walls also seem to disappear, though 
much more slowly. They are at first stretched out and closely 
compressed into a thick and compact band just outside the mega- 
spore membrane. Inasmuch as this band of crushed cells does not 
appear to increase in thickness beyond a certain point, it seems 
reasonable to suppose that it is dissolved and perhaps used by the 
growing gametophyte. Immediately outside of this region of dead 
and empty cells there is a more or less distinct band of cells (figs. 
10, 12, 13, 14) which stain more densely. This band of cells devel- 
ops outward in advance of the gametophyte, keeping much the 
same relation to it as at first. The individual cells have more cell 
contents than the cells outside of the band. Their nuclei take 
basic stains strongly, as sometimes does the cytoplasm also. In 
short, they appear to be undergoing degeneration. The appear- 
ances described are such as have been observed in many other 
plants. The phenomena have been commonly ascribed to the 
effects of the gametophyte. It has been supposed that it secreted 
some sort of enzyme or other substance that diffused outward, 
killed and digested the cells, and prepared them for food for itself. 
It looks like a reasonable inference. 
