CYSTOPUS, OR WHITE RUST. 145 



fungi — viz., the Ascomycdes, yEcidiofuycefes, and Basidiomycetes. 

 All the fungi belonging to this class are characterised by the for- 

 mation of a spore-fruit or sporocarp as the result of the fertiUsa- 

 tion of the female reproductive organ, and differ herein from all 

 those which have hitherto been considered. This spore-fruit 

 consists generally of two distinct parts : a fertile part which is 

 directly derived from the female organ, and ultimately produces 

 true spores, and an investing part, which encloses the spores and 

 occasionally attains a considerable size, as in the Truffle. The 

 sporocarp is derived from a female organ called the " Carpogo- 

 nium." This in the simplest forms is a single cell, closely resem- 

 bling the oogonium of Class III., and the resemblance is still 

 more complete when, as in the case of Podosphcera^ the carpogo- 

 nium is fertilised by a tube growing from the male organ, just as is 

 the case in Saprolegniece. In the majority of cases, however, the 

 carpogonium is multicellular before fertilisation, and its cells con- 

 tribute in different ways to its further development ; some absorb 

 the fertilising substance, whilst others give rise to that part of the 

 fructification which produces the spores, as in the Ascoinycetes. 

 The male reproductive organ occurs in various forms, but fertili- 

 sation is usually effected by a tubular outgrowth. 



Although for the purposes of classification the ^cidiomycetes 

 and the Basidmnycetes are included in this class, the authors 

 acknowledge that no direct proof has yet been given of the 

 existence of sexual organs in either of them, and even in some of 

 the Ascomycetes the sexual organs seem in abeyance. 



Seeking, therefore, fresh information on this subject, we find 

 De Bary, in a recent memoir, proposing a classification of Fungi 

 based on the theory of descent. He considers that, passing from 

 the typical Peronosporcc — viz., PytJiiuni — to the higher Ascomycetes 

 — such as E^ysiphece on the one hand, and to the Saprolegniece 

 on the other — the sexual process is gradually eliminated, and the 

 sexual organs become at first functionless and then disappear 

 altogether. 



In PytJiiiDii itself the antheridium pierces the oogonium wall 

 and fertilises the oosphere by pouring protoplasm into it. In 

 PhytopJitJiora and Peroiwspora the process is essentially similar, 

 but the quantity of protoplasm passed over from the antheridium 



