April, 1907 J Mycological Bulletin No. 76 313 



THE KEY. 



The key which is here presented is a revision, with many additions, 

 of the key printed in the Bulletin of the Torrey Botanical Club, June, 1905. 

 It is based on the study of fresh plants ; but there have been added a 

 few which the writer has not seen, but which have characters so easily 

 recognized, and so different from others, that they were thought worthy 

 of inclusion. This key, like its predecessor, necessarily has many short- 

 comings. As long as we are not sure what American plants are really 

 identical with European ones, and so long as good figures or photographs 

 of the species described for North America, are lacking, we are easily 

 able to mistake the meanings of the descriptions, which are often of the 

 very briefest. Hence this list is merely offered as a slight forward step 

 towards opening up for amateurs the study of this interesting genus. 



Six species, which the writer believes to be undescribed. have been 

 included, although their descriptions have not yet been published. All 

 of them have been collected or been received from various places more 

 than once, and by inserting them in the key, we may be able to help 

 those who continue to come across them. It is hoped soon to publish de- 

 scriptions of them elsewhere. 



It is to be noted that the key has been built largely on the size of 

 the spores. This will necessitate, it is hoped, the study of the plant under 

 the microscope, and so initiate the beginner at once into the proper study 

 of these fungi. We know tliat two different species of mushrooms have 

 again and again been placed under one name because of similar external 

 appearances, when an examination of the spores would have shown a 

 difference of as mucii as 8 microns in some cases. In deciding on the size 

 of spores, the measurement of mature spores only should be taken, which 

 may be recognized by the dark wall or the roughness of the exospore; 

 even in plants with yellowish spores a difference l)etween young and ma- 

 ture spores can be made out. 



KEY TO THE COMMON SPECTE.S OF CORTINARIUS OF EASTERN NORTH AMERICA. 



A. Pileus with a gelatinous cuticle, more or less viscid or glutinous when 

 moist, as is also the stem in some species. (Myxacium and Phleg- 

 macium.) 



a. Pileus coarsely corrugate C. corvngalns Pk. 



aa. Pileus not coarsely corrugate 



b. Surfrice of pileus or flesh distinctly bitter 

 c. Pileus yellow 



d. Glutinous when young, very bitter; stem white 



C. am ants Pk. 



C. vibratilis Fr. 



dd. Not glutinous; stem and gills citron yellow; flesh rather 



bitter: spores 14-17x7-9 C. tiirbinoidcs sp. nov. 



cc. Pileus dark olivaceous to fuliginous, surface bitter.... 



C. infractus Fr. 



bb. Taste not distinctly bitter 



c. Spores large, 9-1 6m long 



d. Stem short, suhcqital or marg'matc-bulhous. spores q-u/j- 

 long. 



e. Pileus heliotrope-purple; gills close, narrow and concolor; 



plant medium size .C. hcliotropiciis Pk. 



ee. Pileus some shade of yellow or greenish 

 f. Gills whitish at first; pileus tinged greenish; stem not bul- 

 bous C. oUvacco-slramincns Kanif. 



ff. Gills yellow to yellowi.sh at first ; stem marginate-bulbous 



g. Bulb top-shaped; gills entire; flesh white C. turbinafus Fr. 



gg. Bulb truncate below; gills eroded, flesh yellow; whole plant 



citron-vellow C. siilfiiriuiis Quel 



