HVMEXOMYCETES... 51 



attached to the substratum by the barren surface, with the 

 hymenium uppermost. 



P. hypnophilus, Berk., and P. chionem, Pers., follow the (6) 

 type ; P. ostreatus, Fr., the various stages of (c) to the highest 

 condition of (d~). Here a^ain, within the range of a single 

 gcims, we have a repetition of what has already been de- 

 scribed as occurring in the Thelephoreae, and also the result 

 of similar external influences, modifying in various ways the 

 inherent epinastic tendency. 



The character of primary importance in distinguishing the 

 orders of the Hymenomycetes consists in the arrangement 

 of the hymenium or spore-bearing surface, which may be 

 briefly described as follows : Agaricineae : hymenium spread 

 over radiating plates or gills. Polyporeae : hymenium lining 

 variously shaped pores or depressions. Hydneae : hymenium 

 covering spine-like or granular projections. Clavarieae : 

 hymenium continuously covering the greater portion of the 

 clavate or variously branched hymenophore. In the Thele- 

 phoreae we find clearly indicated all the above types of 

 hymenium." 



The Tremellineae, although evidently allied to the Hyme- 

 iiomycetes in the presence of basidia, exhibit none of the 

 characteristic sequences of development indicated above, but, 

 as first pointed out by De Bary, connect the true Hyme- 

 nomycetes with the tremelloid Uredines, which are shown 

 by the same author to belong to the Ascomycetes. Hence 

 we must consider the Basidiomycetes as being derived from 

 the Ascomycetes through the Tremellineae as a connecting- 

 link. For a fuller explanation of this subject relating to the 

 evolution of the Basidiomycetes along the lines indicated, the 

 reader is referred to the * Monograph of the Thelephoreae' 

 already alluded to. 



E 2 



