A STUDY OF DEVELOPMENT IN THE GENUS CORTINARIUS 33 1 
elongation takes place in the stem until all the parts are well organized. 
In the mature vStage shown in figure 62, the fruit body is just beginning 
to push up from the tubercle. 
Summary 
1. In the general features of development, these five species of 
Cortinarius are alike. The first differentiation to take place is that 
of a rapidly growing more or less conical region, the stem primordium, 
within the fundamental plectenchyma. Growth and progressive 
differentiation from the apex of the stem fundament gives rise to the 
pileus primordium. Quickly following the appearance of the pileus 
fundament there is developed the fundament of the hymenophore, 
an internal, annular active growth area at the margin of the pileus 
primordium. Growth is centrifugal. The primordial zone is changed 
into that of the palisade and this is transformed into the zone of young 
gill salients. Before the latter make their appearance, a gill cavity 
of considerable size is formed, by the tensions of the rapidly growing 
tissues of this region. The tendency to epinastic growth of the 
pileus margin and the dense crowding of the interpolating elements 
cause the weak fibers of the ground tissue below to become stretched 
and finally broken, leaving the cavity. 
2. The gills are formed in the following manner: The cells of the 
palisade layer increase in diameter. This excess of growth is at the 
same time taken care of by the growth of the subadjacent cells of the 
hyphae, which elongate in radial rows at regularly spaced intervals. 
The gill increases in size by the rapid elongation and increase in 
number of the tramal hyphae, together with an increase in the ele- 
ments of the palisade and subadjacent layer. 
3. In all five species, whether developing a universal veil or not, 
there is present a blematogen layer. This becomes evident as soon 
as the fundament of the pileus and hymenophore appear. Its bound- 
aries at first are very indefinite but in general it represents a zone 
outside the pileus, marginal veil and stem fundaments. Its later 
disposition varies in the five species. In C. armillatus and C. distans 
it enters into the formation of a "universal veil," which separates 
from the surface of the pileus, but it does not form a true volva, or 
teleohlem. In the other species, it becomes consolidated with the 
surface of the pileus ; in C. cinnamomeiis breaking up into fibrils which 
clothe the surface. A very interesting feature of the blematogen is 
