250 BOTANICAL GAZETTE [OCTOBER 
the young fruit body external to the hymenial primordium and con- 
tinuous with what is to be the margin of the pileus above and with 
the undifferentiated stem surface below. The downward growing 
hyphae now take on a different form. They are still slender, but are 
even and blunt and are very densely crowded side by side, are very 
rich in protoplasm compared with the hyphae of the rest of the young 
carpophore and consequently take a deep stain. 
This first growth takes place on the under side of the young 
pileus primordium. The vegetative activity in this region of the 
young pileus is very great, and is very soon extended outward on 
the periphery or margin of the young pileus, as shown by the very 
rapid radial growth of the hyphae at the margin of the pileus, but 
still some distance in from the surface. This radial growth is also 
accompanied by a very strong hyponastic growth, so that the threads 
curve downward, and soon it is so strong that the margin of the pileus 
is strongly incurved, the hyponastic growth appearing to be stronger 
at the margin and near it than further inward. 
At the same time the primordium of the marginal veil increases 
by intercalary growth. In the participation of the hyphae at the 
margin of the pileus in the formation of the veil, they seem to show 
a greater activity in growth so far as the density of the growth and 
richness in protoplasm is concerned; while the larger portion toward 
‘the stem, also increasing by intercalary. growth, becomes looser by 
the rapid elongation of its elements and their partial separation, 
thus forming numerous small air spaces. This seems to have big 
important bearing on the supply of fresh air to the young forming 
hymenium where the air spaces become continually larger, and the 
first air space formed underneath the annular primordium © the 
hymenium not only gives place for the development of the latter but 
also provides aeration. Thus while the veil serves the purpose © 
protection to the young hymenium, its structure is such as to provide 
aeration also, After the differentiation of the hymenial primordium, 
the lateral growth of the pileus is accentuated so that it ie 
broader than the stem portion, and now is formed the external ann 
furrow. Very soon after the hymenial primordium is O ue fe 
the tissue of the pileus primordium, or end of the fruit body, ee 
on a deeper stain in an area extending inward and some depth belo 
