236 
Mycologia 
phores show the structure to be a pseudoparenchyma. The hyphae 
are 3-4 fx in diameter and the cells average 24 /* in length. The 
rhizomorphs are 50-90 fx in diameter. The yellow carpophores are 
easily recognized on the surface of this mat of rhizomorphs, and 
it is almost impossible for one who once knows them to mistake 
them for other pileate forms. The mature as well as the large 
immature carpophores were collected from the same mycelium. 
The only other species of Boletus which is common in this vicinity 
and might be confused with C. Zelleri because of its gregarious 
habit is C. communis, but the writer has never found the latter 
growing in this place, although the spot is often visited by him. 
The material was killed in chromo-acetic acid and stained with 
fuchsin, using picric acid as a destaining agent. This stain gives 
the best results of any tried where a concolorous stain is wanted 
to show differentiation in protoplasmic content. A large number 
of small carpophores of different sizes were collected. The size 
of the carpophores does not necessarily correspond with the degree 
of development, so it is not possible to forecast the stages of 
growth by the size of the plants. The smallest undifferentiated 
fruit bodies sectioned were about 1 mm. in diameter, while some 
of the larger ones were 1.5X3 mm. however, others in which 
differentiation had begun to show plainly, measured 1X2 mm. 
The first stages show no differentiation (Fig. 1). There is no 
indication of a universal veil, either by differential staining or by 
the usual coating of loosely woven hyphae. In fact, as the later 
stages show, there is no veil, either universal or partial ; the carpo- 
phores are thus entirely gymnocarpic and DeBary was correct in 
his inference that some of the Boleti are gymnocarpic. The young 
undifferentiated carpophore elongates vertically and becomes three 
or four times longer than broad. There is no differentiation of 
tissue during this elongation. The carpophore is still a homo- 
geneous mass of hyphae, their general direction being vertical in 
the inner part and parallel with the surface in the peripheral por- 
tion. The first differentiation begins as a superficial, darkly- 
staining, annular region extending around the carpophore a short 
distance from its summit (Fig. 2). This area grows centripetally 
from the periphery and slightly upward, forming what is geometri- 
