58 THE CHICAGO ACADEMY OF SCIENCES 



RUSSULA. 



Hymenophore descending unchanged and forming a vescicular 

 trama; veil none; lamellae rigid, fragile, acute at the edge. Grow- 

 ing on the ground, fleshy, putrescent, with polished stem, and 

 pileus at first or at length depressed. Spores rounded, often 

 cchinulate, white or yellowish. 



1. Pileus without a pellicle, flesh firm, compact 2 



1. Pileus with a pellicle, margin at length sulcate, 



flesh rigid-fragile 5 



2. Flesh extending to the involute margin . . . 3 



2. Flesh not extending to the straight margin 4 



3. Pileus at length black R. nigricans. 



3. Pileus whitish or cinereous-fuliginous. .R. adusta. 



4. Pileus milk-white, then tan-white R. lactea. 



4. Pileus green or yellowish-green R. virescens. 



4. Pileus cinnabar-vermilion becoming pale . . R. rubra. 



5. Lamellae and spores white 6 



5. Lamellae and spores white then yel- 

 lowish . . R. atropurpurea 



5. Lamellae and spores ochraceous 7 



6. Pileus rosy, then blood-color R. emetica. 



6". Pileus toast-brow^ then pale-tan R. pectinata. 



7. Lamellae free, broad, somewhat dis- 

 tant R. alutacea. 



7. Lamellae adnate, narrowed behind, 



much crowded R. puellaris. 



7. Lamellae adnate, subdistant R. ochrophylla. 



7. Lamellae slightly adnexed, broad, not 



crowded R. ochracea. 



Russula nigricans Fr. 



Pileus olivaceous-fuliginous, at length black, fleshy to the 

 margin which is at first bent inwards, convex then flattened, 

 umbilicate-depressed, when young and moist slightly viscid and 

 even, but without a separable pellicle, at length rimose-squamu- 

 lose; flesh firm, white, when broken becoming red on exposure to 

 the air. 



Lamellae rounded behind; slightly adnexed, thick, distant, 

 unequal, paler, reddening when touched. 



Stem persistently solid, equal, pallid when young, at length 

 black. 



Spores papillose, 8 /x. Pileus 5 to 10 cm. broad, stem 2.5 cm. 

 thick. 



Woods, Glencoe. August. The entire plant turns black in 

 drying and the surface cracks into areas like that of R. virescens. 

 Russula adusta Fr. 



Pileus pallid, whitish or cinereous-fuliginous, equally fleshy, 

 compact, depressed then somewhat infundibuliform, margin at 

 first inflexed, smooth, then erect, without striae; flesh unchange- 

 able. . 



