The development of Armilloria mellea 
110 
of the hyménium, the pileus end of the carpophore does not show any 
differential staining in the specimens I have seen, though its elements 
are of a finer composition than the piliferous outer layer, as described 
above. Very soon, however, the tissue of the young carpophore in the 
end above the hymenophore primordium begins active growth and the 
liyphae are richer in protoplasm. This region, which is the pileus pri¬ 
mordium, thus shows differential staining by taking a much deeper tint 
than the peripheral layer of radiating hyphae. These hyphae become 
somewhat longer and stouter and as the pileus grows older those toward 
the margin turn more and more downward and come to lie radially on 
the surface. 
The tissue of the veil becomes loose providing for aeration of the 
hymenophore. The piliferous layer (including the outer portion of the 
pseudoparenchyma), which forms the rudiment of the veil and clothes the 
young carpophore, probably represents the “universal veil”. As the 
carpophore becomes larger this “universal veil” can be recognized for 
some distance down on the stem as a looser layer, although now the 
hyphae are no longer radial in this region. Just inside of this the outline 
of the stem cortex can often be seen, indicated by a deeper stain. As 
the veil grows it appears to be added to also in some cases by the 
growth of hyphae from the upper part of the stem, the hyphae often 
growing close up under the young hymenophore and then curving down¬ 
ward and outward. The position of the veil with reference to its being 
close up in the gill cavity or at some distance away seems to vary. 
Sometimes it is as described by Hoffmeister, but it is too variable to 
permit of assigning to it a definite position and a definite angle in the 
direction of the threads composing it. In a few cases the loose hyphae 
which form the “universal veil” down on the stem, seem to be separated 
from the young stem cortex by a thin layer which seems to be in a 
partial state of gelatinization, and higher up next the gill cavity threads 
from the stem cortex pass over outward and unite with the portion from 
the “universal veil”. 
Later stages in development than those presented in the figures 
were not studied in microtome sections, nor for the purpose of this article. 
The further development of the hymenophore probably offers nothing 
unusual and the early stages of the origin of the gill folds are figured 
by Beer (1. c.). But it is well known that Armillaria mellea is a very 
variable species not only in the size of the carpophores but in the cha¬ 
racter of the surface, being described as smooth or scaly, the latter form 
with pointed tufts of scales particularly abundant and strong over the 
center of the pileus probably being the more common form. The annulus 
also varies greatly, from thin and membranous to tumid, and with a 
duplex margin. How the annulus becomes so very thick as it sometimes 
is in mature specimens, would be interesting to determine, i. e., whether 
in some examples it is quite stout from the first, with the primordium 
of the hymenophore of much deeper origin than found by Beer or myself, 
or whether there is a very great increase in the tissue of the marginal 
veil after its differentiation. 
