116 
G. F. Atkinson, 
veil, the reasonable conclusion being that in Armillaria mellea with a 
marginal veil, also, the hymenophore has an endogenous origin. There¬ 
fore, although Beer is correct in his interpretation of A. mellea , it seems 
desirable to present convincing evidence from the material of A. mellea 
alone, of the origin of the hymenophore. In connection with this we 
may well call attention to some peculiarities in the structure of the 
young carpophore which are not treated of by Beer in the paper refer¬ 
red to. 
The young fruit bodies of A. mellea vary considerably in form 
according to the conditions under which they are developed. Sufficient 
observations have not been made to state, with any degree of assurance, 
just what the correlations of form and conditions are. But it appears 
probable that where the rhizomorphs are more or less exposed, that is, 
very near or at the surface in a somewhat firm substratum, the very 
young carpophores are “bulbous”, having a stout bulb or base, from the 
upper surface of which the minute pileus and stem are developed, very 
much as in certain large species of Lepiota , as L. rhacodes, etc. Under 
other conditions where the substratum retains more moisture and the 
young carpophores are protected for some time, they are slender and at 
the earliest differentiation of the pileus it is equal in diameter with the 
base of the plant. Such young carpophores are nearly cylindrical or ob¬ 
long in outline. Most of the forms which I obtained for sectioning were 
of the latter type, the others being already too far advanced when collected. 
It would appear from the figures presented by Beer that most of his 
carpophores were of the “bulbous” form. 
The youngest carpophore sectioned was about 0,5 mm in diameter. 
It appears that at a very young stage the primordium of the carpophore 
is differentiated into three regions, especially the upper portion where later the 
differentiation of pileus and stem takes place (fig. 1). At just what stage 
was not determined. There is 1 st an outer zone of radiating hyphae; 
2 nd , an illdefined cortex; and 3 rd , a central core of undifferentiated 
tissue. The cortex is more conspicuous over the part later marked off 
as the pileus, though the primordium of the pileus cannot yet be regarded 
as differentiated from the stem. 
The radial hyphae of the outer zone in the youngest fruit body 
studied are 60—100 ^ long by 6—8 /u in diameter. They are septate, 
the cells usually 12 u to 20 /u long or rarely some are 30 or 40 ( u long. 
They soon become constricted at the septa, especially from the middle 
region toward their free ends, the cells becoming elliptical to subglobose, 
10 to 15 or even 20 fi in diameter in the older specimens. They taper 
gradually to the narrower base where they arise from an irregular cortex 
of radiating cells gradually merging into a pseudoparenchyma of elongated 
cells, the cells irregular in length and form, but 3—6 ju in diameter. The 
radial hyphae stain rather deeply, more so than those of the cortex or 
middle zone, which itself is stained more deeply than the central zone. 
The protoplasmic content as well as the thick walls take the stain. These 
hyphae are quite characteristic, as Hartig has remarked, for they are 
present in older specimens where they are even more characteristic. The 
tissue of the central zone adjacent to the inner portion of the cortex is 
similar to it in .texture but very faintly stained. Farther within the 
hyphae are in a more or less longitudinal direction in the core, curving 
