22 
GEORGE F. ATKINSON 
"universal veil," as its outer surface, but the bulk of it is formed by the growth of 
threads from the margin of the primordial pileus and increase of its own elements. 
The duplex character is beginning to show, the lower portion showing a more open 
mesh, increase having come chiefly from growth of fundamental tissue between the 
blematogen and stem surface. 
Fig. 6. Section of a somewhat older carpophore of Ag. arvensis, the gill cavity 
slopes downward still more due to continued epinasty of the pileus margin and the 
elongation of the stem; the duplex character of the veil is more distinct; the bulb 
of the carpophore has broadened greatly but has not elongated appreciably so that 
the stem surface here is horizontal while the main part of the stem is elongating, 
which brings the surface nearer a perpendicular position. The open mesh character 
of the medulla is beginning to show due to a lagging behind in growth. The primor- 
dial surface of the pileus has become concrete with the inner zone of the blematogen, 
or "universal veil," so that its outer zone really becomes the surface of the mature 
pileus. 
Fig. 7. Section of a young carpophore of Ag. comtulus showing in the upper 
portion the roundish primordial area of the pileus, on either side the more densely 
staining primordium of the hymenophore and pileus margin; below the nascent 
primordium of the stem, enveloping stem and pileus fundaments, is the coarse-meshed 
blematogen, or "universal veil." 
Fig. 8. Ag. arvensis, highly magnified portion of fig. i showing details of struc- 
ture and differentiation in the region of the early primordium of the hymenophore and 
pileus margin. This is located at the intersection of lines perpendicular to a, a. At 
the right note the coarse-meshed tissue of the blematogen with its thick-walled 
hyphae, in strong contrast with the dense area at the left with thin-walled hyphae. 
At the angle of this tissue (intersection of lines from a, a) note curving downward of 
the elements of this primordium. The open-meshed tissue beneath is the beginning 
of the gill cavity, and the threads of this tissue form the primordium of the inner 
portion of the partial veil; the hyphae are thin-walled and distinct from those of the 
blematogen lying outside. 
Fig. 9. Ag. arvensis. Highly magnified portion of a section from the same 
carpophore as fig. 2, showing young gill "slit," the hymenophore primordium just 
above; the primordium of the pileus margin above and slightly to the right, at inter- 
section of perpendicular lines from h, b; on the right the open-meshed tissue of the 
blematogen, or "universal veil," below the margin of the pileus and the gill "slit" 
is the now more abundant tissue of the partial veil of finer texture than that of the 
blematogen. 
Fig. 10. Ag. comtulus. Section of well advanced carpophore, showing the 
hymenophore primordium with nascent lamellae; the distinct primordial margin of 
the pileus, the less differentiated area of the pileus primordium above; the loose 
meshed blematogen, or "universal veil," the well advanced partial veil of duplex 
structure below the gill slit covered externally by a section of the blematogen; the 
conical primordium of the stem below. 
Fig. II. Ag. comtulus. Section of a nearly mature carpophore, slightly 
tangential, showing nearly mature lamellae; duplex partial veil; surface of stem; 
and pileus surface "concrete" with the "universal veil," or blematogen; a section of 
the latter forms one-third to one-half the thickness of the portion of the partial veil 
extending from margin of pileus to its junction with the lower portion. 
