CARPOASCI. 169 



■contain many asci, and the envelope is pierced by a definite 

 aperture. 



Brefeld endeavours to explain the ascooarp of the Erysipheae from the 

 «porangial structures of the Zygosporeae (Hhizopus and Mortierella); De 

 Bary' and Zopf,^ on the other hand, see in it an oosporangium, like that 

 of the Oosporeae. Under this latter view the envelope of the Carpoasci is 

 morphologically homologous to the antheridia of the Saprolegnieae and 

 Peronosporeae. In the latter group the antheridium generally takes the 

 form of an open fertilization-tube, in the Saprolegnieae it remains closed, 

 and is physiologically no longer an antheridium. Zopf found in one of 

 the Saprolegnieae {Dictyuchus carpopkorus), an envelope resembling that 

 of the Erysipheae, and on this ground he, along with De Bary, links the 

 Erysipheae to Oomycetes like Aehyla through forms like Podosphaera. 



The reproductive cells or ascospores result from direct nuclear 

 division inside the asci. They are generally simple and uni- 

 cellular, but it is not uncommon to find that, by the formation 

 of cross and longitudinal walls, each spore forms a cell aggre- 

 gation (sporidesm of De Bary), v^ith each cell capable of 

 germination on its own account. The number of cells in each 

 aggregation, as well as the size and shape of each cell, are in 

 many cases constant, and form points for the determination of 

 species. Appendages to the spores are characteristic of many 

 species. 



The Carpoasci possess, in addition to ascospores, other 

 means of reproduction. Thus, thick-walled chlamydospores occur 

 either in the mycelium as resting-spores {Hypomyces), or as 

 spores (oidia) resulting from a breaking-up of hyphae. 

 Many kinds of conidia may also be produced, some from the 

 germinating ascospores, some abjointed from a branch of the 

 mycelium or from some form of special conidiophore. These 

 latter may be produced isolated, or massed together in hollows 

 of the stroma, or in closed structures resembling ascocarps, 

 and called pycnidia. The various forms of reproductive organs 

 presented by each species will be more closely considered as 

 we proceed. 



The Carpoasci are arranged, according to the structure of 

 the ascocarps, under the following divisions : — the Peris- 

 poriaceae, Pyrenomycetes, Hysteriaceae, Discomycetes, and Hel- 



' De Bary. Seitrage z. morph, u. Phyuol. d. Pike. 



^ Zopf. Beitrdge 2.. Physiol u. morph. neider Orgaiiismen. Heft 3, 1893. 



