BASIDIOMYCETES 411 



would have made possible a many-fold increase of their spore production. 

 The critical point for the differentiation of the hymenophore seems to lie 

 more in the fact that the lateral elongation of the fructification is limited 

 in nature by practical bounds (especially in the stipitate forms, by the 

 static moment) and that, with the increasing development of the angio- 

 carp, the surface necessary for spore formation is forced into narrower 

 limits. Thus, this differentiation of the sporiferous layer reaches its 

 maximum in those forms where, as a result of the development of the 

 fructification (maturity), a supplementary enlargement of the ground plan 

 is no longer possible. 



The effectiveness of this principle of folding is shown by the following 

 coefficients (Buller, 1909) : in Russula citrina the hymenial surface is 

 seven times larger than it would be if the hymenophore on the lower side 

 of the pileus were smooth; in Amanita rubescens ten to twelve, Armillaria 

 mellea about thirteen, Hypholoma sublateritium seventeen to eighteen, in 

 Psalliota campestris about twenty, Fomes igniarius about thirty-eight, 

 F. applanatus about 164, etc. In these last forms, one must also remem- 

 ber that the fructifications are perennial and each year form a new hyme- 

 nial layer over the old one so that their coefficient increases in geometric 

 progression. Thus the numbers of spores is enormous : a cap of Polyporus 

 squamosus produces over 100 billions of spores per annum. At the time 

 of spore production it discharges at least a million spores a minute and 

 continues this production through several hours or days. 



The Basidiomycetes (as the Ascomycetes) fall into two groups 

 according to the development of the sporogenous parts. In one group, 

 the basidia develop irregularly throughout the sporiferous tissue, as do 

 the asci in the Plectascales ; this group presents no peculiarities. In the 

 other groups, the basidia develop to uniform, palisade layers, i.e., to 

 hymenia. This second group may be divided into two types; in the first 

 type the parallel hyphal ends forming the fundaments are not themselves 

 transformed into basidia but they remain sterile and form their own layer 

 of paraphyses; the basidia are distributed in the subhymenial tissue 

 and grow singly through the layer of paraphyses forming a continuous 

 layer rather late (e.g., Fig. 343). In this type the sequence of paraphy- 

 ses in time and space (looked at from incongruence of the cytological 

 development of the paraphysis) conforms with the hymenium of the 

 Discomycetes and suggests Exobasidium (p. 532) in which the new basidia 

 arise directly on the secondary mycelium and gradually force their funda- 

 ments between the older basidia; consequently, it is regarded as primitive 

 and is called the protohymenial type (Maire, 1902). 



In the second type, the collective development of the parallel hyphal 

 ends proceeds at a uniform rate (Fig. 294). As this type has developed 

 the individual characteristics of the Basidiomycete hymenium, it is 

 called the euhymenial type. The hyphal ends of its young hymenial 



