1906] ATKINSON—AGARICUS CAMPESTRIS 263 
Fic. 4. Young carpophore, var. Alaska, with endogenous primordium of 
hymenium a little more advanced than in fig. 3; anyones veil distinct as a loose 
definite layer of tissue surrounding the carpophore; oc. 2, obj. 16™™. 
Fic. 5. Young carpophore, var. Columbia, Bae ee endogenous primordium 
of hymenium a little more advanced than in fig. 4; universal Mas as a very thin 
layer; oc. 2; obj. 16™ 
PLATE VIII, 
Fic. 6. From young carpophore, var. Columbia; at stage when gill slit is 
just forming, showing sharp-pointed threads of primordium of hymenium pro 
jecting downward; also shows at the right the thin layer of universal veil; about 
same gee as fig. 7, but not with Zeiss microscope. 
1G. 7. Same object as fig. 6, but showing only the gill slit and primordium 
of bismacicn: 
Fic. 8. Same as figs. 6, 7, but more highly magnified; oc. 6, obj. 3™™. 
PLATE IX. 
Fic. 9. Young carpophore, var. Alaska, showing endogenous primordium of 
hymenium on le side, about the same stage as fig. 4, but higher magnification; 
9c. 4, obj. 1 
FIG. to. a carpophore, var. Alaska, with endogenous primordium 
more advanced, showing definite and clear opening, the descending threads of 
the primordium of the lamellae, loose tissue of the inner veil, and primordium 
of stem cortex, outlined as an oblique area of younger threads rich in fee 
extending from opening obliquely downward and outward; oc. 6, 0 
1G. 11. Portion of young carpophore, var. Columbia, yi gill slit; 
young lamellae in longitudinal section, inner veil of more open loose tissue; 
shows also how primordium of hymenium continues in its development as mar- 
gin of pileus continues to grow; cortex of stem well-formed, showing as a more 
Compact tissue over the surface to which the veil is attached; oc. 4, obj. 16™™. 
Fic. 12. Portion of young carpophore same age as fig. rz and from same 
plant, but cut somewhat obliquely so that a number of gills are shown in eo 
Section, otherwise as in fig. 11, but with less magnification; oc. 2, obj. 16™™ 
PLATE X. 
Fic 13. Cluster of young carpophore, var. Columbia; numerous very young 
ones, several in the large button stage, showing the small white patches of the 
universal veil on the brown cuticle of the pileus. 
Fic. 14. Another cluster of young carpophores, 1 var. Columbia, showing nu- 
merous very small ones, and several of the small button stage, the universal veil 
Separated into a few large white thin patches; rhizomorphs in the substratum. 
PLATE XI. 
Fic. 15. Longitudinal section of young carpophores magnified twice the real 
length, showi ing endogenous primordium of hymenium, gill slits, veil, and the 
primordium of cortex of stems. 
