508 CLASS BASIDIOMYCETEAE 



such as have been found of so great importance in the Polyporaceae. 

 Fayod (1889) and others (Karsten, Heim, Singer, etc.) have emphasized 

 more and more the necessity of basing the generic distinctions upon these 

 anatomical and chemical characters. The type of gill structure as empha- 

 sized by Fayod, the amyloid or nonamyloid character of the spore wall, 

 the structure of the cuticle of the pileus, the presence or absence of clamp 

 connections, all these have proved to be of great importance. Just how far 

 these characters should be used in distinguishing genera or whether they 

 should only be used for lesser units of classification is not yet agreed upon, 

 hence the above-noted great differences in the number of recognized 

 genera or even families. 



The characters of size — of spores, cystidia, pilear hyphae, etc., as well 

 as of the whole spore fruit — are not always reliable. Thus Togashi and 

 Oda (1934) showed that the age of the pileus has considerable effect upon 

 the spore size. In Armillariella mellea and in Pholiota adiposa (Fr.) Quel, 

 the length and width of the spores shed on the fourth day were 12 to 15 

 per cent less than of the spores shed on the first day from the same sporo- 

 phores. On the other hand Collyhia velutipes (Curt.) Fr. {Myxocollyhia) 

 does not exhibit any such change in spore size with the age of the pileus. 

 The size and even the shape and color of the pileus, and sometimes of the 

 gills, depends considerably upon the temperature, humidity, and illumina- 

 tion, and to a large degree upon the amount of food available in the sub- 

 stratum. The position of the stipe, whether central, eccentric, or lateral, 

 may vary in the different spore fruits growing from the same tree or log, 

 depending upon the position of the point of exit from the host. If this is 

 from the top it may be centrally stipitate and from the side the stipe may 

 be eccentric or lateral. 



In general the spores may represent four rather distinct types: (a) 

 With an endospore and epispore, often with a distinct germ pore. Such 

 spores are mostly ellipsoidal or short cyhndrical, or oval, and are often 

 somewhat truncate at one end. (b) With only one spore wall layer visible, 

 usually subspherical, oval, elhpsoidal or cyhndrical. (c) Very strongly 

 angular or with large knobs. Spores of this type are mostly rose-colored to 

 pink, (d) More or less ellipsoidal or oval or cylindrical with mostly six or 

 eight longitudinal grooves so that in cross section they are not round but 

 angular or lobed. These spores also are more often rose or pink. The outer 

 surface of the spores of all types may be smooth (more often the case) or 

 somewhat roughened or tuberculate or reticulately marked by ridges. 

 These tubercles or ridges are stained blue by iodine reagents in amyloid 

 spores such as occur in species of Russula and Ladarius. 



The angiocarpic spore fruits such as those of Amanita show an external 

 universal veil or cortex before they open. Upon completion of the expan- 

 sion the portion of this veil on the upper surface of the pileus may be 



