18 BOTANICAL GAZETTE [JULY 
tissue as the latter is from the megaspore. Fig. 48 is a more 
magnified section of the same spore and tissue. A small amount 
of granular material appears between the spore and the large- 
celled tissue, but the inner walls of the latter are apparently 
intact. A few cases were found, however, where the innermost 
of the large cells seemed to be partly broken up on the side 
next the spore. At the stage shown in fig. 49 the existence of 
so definite a layer around the spore is doubtful. The cells 
adjoining the spore are still larger than others beyond them, but 
in all cases that I have found they are more or less separated 
from each other and approach in appearance the loosened 
‘spongy tissue” which has been described in other cases. In 
later stages, however, there constantly occurs a single layer of 
very large rectangular cells lying next to the megaspore, while 
beyond those the ordinary nucellus-tissue is crushed and dis- 
organized. fig. 51 shows such a layer around a large spore 
before the formation of the cellular prothallium. The large 
cells seem perfectly intact ; walls are present on both sides and 
the nucleus is large, has an abundant reticulum, and is more 
like what would be expected in an actively secreting cell than ina 
rapidly disorganizing one. Figs. 52 and 53 show the same layer 
at a later stage, just before the prothallium has reached its full 
size. In fig. 52 the wall of the megaspore has shrunken some- 
what and the large cells have become more elongated and 
slightly separated. The layer of large cells and two or three 
layers of ordinary cells beyond it are always furnished with 
starch during the growth of the prothallium; the starch is con- 
tinually accumulating in the further-removed cells as the inner 
ones are being disorganized. The large-celled layer is also 
destroyed at the last moment and the mature prothallium is sur- 
rounded at its upper end with four or five layers of ordinary 
nucellar cells. In the Abieteae the young germinating mega- 
spore is imbedded in a loose tissue which resembles somewhat 
the large-celled tissue just described in Taxodium. Its limits 
are so distinct that Hofmeister (62) mistook it for endosperm. 
In comparing Strasburger’s (’79) figures of such tissue in Pinus 
and Lai with my figs. 45 and 47 in Taxodium, it will be ‘seen 
eee eT 
