156 THE AGARICACEAE OF MICHIGAN 



narrow, adnate, close, broader in front, equal or few shorter, few 

 forked, interspaces venose. STEM white, never red, equal or sub- 

 equal, spongy-stuffed, somewhat slender, fragile, hollow, even, 1.5 

 cm. long, 1-1.5 cm. thick. SPORES pale yellowisli-ochraceous, sub- 

 globose, echinulate, 8-9 micr. TASTE very acrid. ODOR none. 



Scattered or gregarious. Oak and maple woods of southern Mich- 

 igan. July and August. 



This represents a group of red Russulas with acrid taste and gills 

 varying pale ochraceous or somewhat yellowish in the different 

 forms. I have limited the name to those with white stem and a 

 rather firm and hardly striate pileus, although it may include sev- 

 eral forms of which only the spore-color has so far been a dis- 

 tinguishable character. The separable, viscid, distinct pellicle and 

 rather fragile stem, relates it to the Fragiles. From R. tenuiceps 

 it is separated by the less deep ochraceous spores and gills, the 

 firmer consistency of pileus and gills, and the uniform red color and 

 even margin of the pileus. 



136. Russula tenuiceps Kauff. 



Mich. Acad. Sci. Rep. 11, p. 81, 1909. 

 Illustration : Plate XX of this Report. 



PILEUS 7-12 cm. broad, thin, fragile, convex to expanded, the 

 somewhat viscid pellicle easily separable, margin at first connivent, 

 striate, deep rosy-red or blood-red, sometimes white, spotted or 

 tinged with orange blotches, sometimes uniform red, with or without 

 minute rugae. FLESH white, red beneath the cuticle, very fragile 

 at maturity. GILLS white, then yellow-ochraceous, crowded, nar- 

 row, fragile, narrowly adnate to free, few forked, interspaces 

 venose, equal. STEM fragile, white or rosy-tinged, spongy-stuffed, 

 subequal or ventricose, obscurely rivulose, white within and un- 

 changed, 5-9 cm. long, 2-2.5 cm. thick. SPORES yellow-ochraceous, 

 subglobose, 6-8 micr.. echinulate. TASTE acrid, sometimes tardily 

 but very acrid. ODOR not marked. 



Gregarious. Mixed woods at Marquette; in oak and maple woods 

 at Ann Arbor. July and August. Rather frequent. 



As in R. veternosa, it is probable that several forms are repre- 

 sented here. The red Russulas are very troublesome, and we seem 

 to have a considerable number of forms with acrid taste and yellow- 

 ish to deep ochraceous gills, which cannot be easily kept separate. 

 All efforts to refer- them to old species like R. sardonia, R. rugulosa, 



