3S4 



THE BASIDIOMYCETES 



because they form mycorrhizae, mainly on forest trees. A few 

 are pathogenic; Amiillaria mellea on orchard and forest trees 

 [Thomas (1934)] and Marasmhis sacchari on the roots of sugar 

 cane are the best-known parasitic species. Nyctalis asterophora 

 and N. parasitica parasitize other agarics. 



Marasjnius saramentosiis causes "horse-hair blight" of cacao in 

 the tropics, and other species of this genus also are known to 



cause thread blights of forest 

 trees. Marasmius crinis-eqid 

 is not uncommon on oaks in 

 the Gulf Coast states. 



The fructifications vary 

 greatly in size and durabilit\^ 

 Those of some species of My- 

 cena may have pilei a few 

 millimeters in diameter that 

 are very ephemeral. Schizo- 

 phylliim cormnune, which is 

 quite leathery, can be dried 

 repeatedly but revives on be- 

 ing- moistened. In fact, it is 

 remarkably adapted to xero- 

 phytism. Agariciis arvensis 

 may have pilei 40 cm in di- 

 ameter. The fructifications 

 of AjJtanita solitaria attain a 

 height of 30 cm with pilei 20 

 cm in diameter. The shagg\- 

 mane mushroom, Coprimis 

 comatiis, has been recorded 

 to have fructifications 36 cm 

 tall and pilei 25 cm in circumference. 



Development of basidiocarps among agarics. The develop- 

 ment of basidiocarps among gill fungi is none too well under- 

 stood, mainly for the reason that relatively few species have been 

 studied. The status of this subject can best be appreciated from 

 examination of reports by Atkinson (1906, 1914, 1914a, 1914b, 

 1916), Douglas (1916, 1918, 1920), Sawyer (1917, 1917a), Moss 

 (1923), and Hein (1930). 

 The fruit bodies of gill fungi are commonly called mushrooms 



Fig. 138. Diagrammatic sections ot 

 developing basidiocarps of Mycena 

 subalkali?ia, of gymnocarpous type. 

 A. Undifferentiated "button." B. Ini- 

 tiation of pileus at apex of stipe. 



C. Hymenial surface becoming ap- 

 parent at lower edge of young pileus. 



D. Lamellar development has pro- 

 gressed, and margins of pileus are 

 rolled inward toward the stipe. 



E. Development of lamellae is well 

 advanced. (Adapted from Douglas.) 



