DEVELOPMENT OF EXOGENOUS SPECIES OF AGARICS 
49 
caused by the crowding of the palisade tissue and the pushing down- 
ward of the pahsade layer by the elongation of the subadjacent tissue 
in regularly spaced intervals (figs. 130-134). As these folds develop, 
their surface becomes again uneven (fig. 139) as it did in case of the 
Hygrophorus forms mentioned above. Figure 135 represents a fruit 
body which is nearly mature. In figure 136 one may observe the 
spores from a mature plant. As in all the characteristic species of 
Entoloma the spores are angular. In this species they are very nearly 
cubical. 
Summary 
1. The fruit bodies of these exogenous forms come from buttons 
composed of interwoven hyphae, mainly extending in a longitudinal 
direction; with the exception of the surface layer, which is sometimes 
transformed by substances in the substratum through which the plants 
are growing, the tissue is entirely homogeneous. 
2. Differentiation of the pileus and stipe primordia is brought 
about by growth at the apex of the fruit body. The hyphae multiply 
by profuse branching and begin to turn outward. This soon results 
in an enlarged pileus fundament, differentiated from that of the 
stem by an annular furrow. The tissues of both regions remain 
homogeneous in character throughout the life of the plant. 
3. The fundament of the hymenophore is differentiated in the 
annular furrow. In the three Hygrophorus species, it seems to appear 
simultaneously with the differentiation of the pileus and stipe primor- 
dia, while in those of Mycena suhalcalina and the three Entoloma ones, 
it develops slightly later. It is characterized by crowded, narrow, 
usually pointed hyphae and by an irregular surface. 
4. Before the formation of gill salients an even palisade layer is 
usually formed by dense, broader hyphae with blunt ends. In two 
Hygrophorus species, H. miniatus and H. nitidus, however, the surface 
does not become even until after the gill ridges have formed. 
5. The gills are formed from salients which appear first at the stem 
and develop in a centrifugal manner to the margin of the pileus. 
The dense crowding of the elements of the palisade layer results in a 
strong tension of the tissues, which is finally taken care of by the 
development of the subadjacent tissue downward into regularly spaced 
radial ridges. This method is precisely the same as that described 
by the early workers (11, 12, 13, 14, 17, 18, 19) and by Blizzard (9) 
