PEZIZALES 353 



of the Pezizales, ascogonia are no longer formed and the ascogenous 

 hyphae develop directly from the generative or vegetative hyphae. 



In the lichens pure amphimictic forms (of the Ascobolus magnificus 

 type) are still unknown, but our acquaintance begins with the first stage 

 of degeneration of the Ascobolus carbonarius type. It may be again 

 emphasized here, however, that these relationships are generally otherwise 

 interpreted, namely, as in favor of a derivation from the Florideae. 

 As we shall again meet similar phenomena in the Laboulbeniales, the 

 discussion of the various theories of derivation of the Ascomycetes will 

 be deferred to the review at the close of the Laboulbeniales. The Pezi- 

 zales here show a very heterogeneous arrangement which begins with the 

 lower forms rooting in the Plectascales and Myriangiales and rises above 

 the Polyporaceous type to highly differentiated agaricaceous forms. The 

 sexual organs connect directly to the antheridia and ascogonia of 

 the Gymnoascaceae and Aspergillaceae and proceed to a further morpho- 

 logical development. Then the antheridia degenerate and the original 

 gametangial copulation is replaced by deuterogamy, first by parthenog- 

 amy, then by autogamy and finally, after the ascogonia have disappeared, 

 by pseudogamy. With this degeneration of sexuality the ascogenous 

 hyphae gradually lose their special character and change their form by 

 fusion of the hook tip with the stipe cell and a further outgrowth of the 

 hook to a clamp mycelium which penetrates the fructifications for long 

 distances. 



