240 THALLOPHYTES. 



number of hyphae, their spore-bearing branches grow close to one another and form 

 level expansions called llymenia ; the separate fertile branches standing vertically 

 upon the hymenial surface. According as the hymenium is formed upon the 

 surface or in the interior of the receptacle, this latter is termed gymnocarpous or 

 angiocarpous. The hymenial surfaces are generally greatly extended, and their 

 form is highly characteristic of distinct groups of Fungi {vide infra under Gastro- 

 mycetes, Hymenomycetes, Discomycetes). The hymenia never produce anything 

 but asexual reproductive cells, the Spores; but the hymenium-bearing body itself 

 may be the product of a sexual process (as in Peziza). 



The mode of Reproduction of Fungi is even more various than that of Algas. 

 In those species the cycle of whose development is fully known, sexual and asexual 

 reproduction occurs, or the latter is replaced by conjugation. In those cases where 

 neither sexual reproduction nor conjugation has hitherto been observed, it may be 

 assumed that our knowledge of the series of development is still incomplete, and 

 that forms which are at present considered independent are really only members 

 of an alternation of generations. The influence of the different modes of repro- 

 duction on the whole course of development and on the whole manner of life of 

 the particular species is however so various that it does not permit a comprehensive 

 description (as may be seen by comparing the examples below). It is important 

 to note that it has been already ascertained that in many Ascomycetes the recep- 

 tacles which bear the Ascospores are the result of a sexual process which takes place 

 in connexion with the mycelium, so that the mycelium forms the first sexual, the 

 receptacle the second asexual generation. In the Phycomycetes, on the other 

 hand, the product of the sexual process is a resting cell (oospore or zygospore) ■ 

 similar to what is found in many Algae; while the origin of the receptacle of the 

 Ascomycetes corresponds essentially with that of the Floridese. The spores pro- 

 duced asexually are very different in their origin and form ; and in many Fungi 

 two, three, or even four different forms of spores have been observed within one 

 cycle of development. But since these relationships can only be made clear by 

 examples, those facts only which are most important for nomenclature will be 

 here mentioned. In several Phycomycetes swarm-spores are formed which, how- 

 ever, are wanting in all other Fungi. The motionless spores are either simply 

 detached from the end of a branch of the hyphae which is termed the Basidium, — 

 and this detachment may be often repeated so that a basidium produces a chain 

 of spores, — or the spores sprout from the basidium as short swollen separable 

 branchlets, either successively or simultaneously (in this case in twos, fours, or 

 larger numbers). This formation of spores depends finally on bipartition of the 

 basidium. Essentially diff"erent from these Basidiospores ^ are the Ascospores, 

 w^hich arise by free cell-formation in the protoplasm of the sac-like swollen terminal 

 cell (Ascus) of a branch of a hypha. With the development and escape of the spores 

 the ascus disappears. Both the basidiospores and the ascospores, which often 

 arise in the cycle of development of one species, may break up by subsequent 



^ To this category belong also the Sperinada, very small spore-like structures, which are mostly 

 produced in large numbers by the Uredinece and Ascomycetes; their function is, however, 

 unknown. 



