[Vol. 2 



674 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



corded. This latter procedure is entirely commendable, but 

 it has been so much abused that the spore characters carried 

 in the literature are far from being: reliable 



g ll-llttUlV, XXX IX *«*» 



!-> 



ber of cases. However, allowances must be made for some 

 variation in measurement by different individuals as no two 

 persons will report exactly the same measurements for one 



species. 



The shape of the spores is probably subject to somewhat 

 less variation with age than is the size. Spores begin to take 

 their characteristic shape while they are yet comparatively 

 immature and from seeing such a spore one can judge of its 

 mature form more accurately than of its mature size. Often 

 the spores of two or more species are so similar in shape that 

 it is perhaps best not to try to distinguish between them, al- 



1 the distinction may be perfectly apparent to one who 

 has before him the spores of all the species in question. The 

 terms used to describe spore forms are not as rigidly denned 

 as we could wish, and it does not add to the clearness of dis- 

 tinction between two species to describe the spores of one as 

 ''elongate-ellipsoid" and of the other as " narrowly fusoid" 

 and expect the users of the manual to distinguish the species 

 on that basis. There are many cases, however, where the 

 form of the spores may be used to good advantage. 



Spore markings are so universally absent in the Polyp- 

 oraceae that the subject requires very little comment here. 

 There are probably not more than a dozen species that are 

 characterized in this way and they are so widely separated 

 that the character is given an added value. In some groups 

 of the fungi, especially among the Ascomycetes, not only the 

 presence or absence of markings on the spore wall but also 

 the nature of these markings is taken into account. 



Cystidia. — Cystidia may be defined as more or less con- 

 spicuous sterile organs found either in the hymenium or in 

 the subhymenial tissue of various basidiomycetous fungi. 

 They are usually unicellular and they may be smooth or they 

 may have a more or less incrusted surface, the incrusting 

 substance probably always being calcium oxalate. The name 

 ' ' setae ' ' has been given to these bodies when they are colored 



