3o8 THALLOPHVTES. 



species of Fungi, I will simply endeavour to illustrate the characteristics of the three 

 principal groups above-mentioned by giving a complete account of such forms 

 as have been accurately described by reliable observers, laying especial stress upon 

 the more important features of their life-history. 



A. The Ascomycetes. 



In the fructification of the Fungi belonging to this group there arise from the 

 ends of the fertile ascogenous hyphae cells of a club-shaped or spherical form (asci), 

 from the protoplasm of which numerous spores {ascospores) are developed by free-cell- 

 formation ; usually a definite number of these spores, either four or eight, occurs 

 in each ascus. The fructifications are either open {apothecia) or more or less com- 

 pletely closed {pertihecta). 



The spores always possess a firm cuticularised external membrane, the exo- 

 spore, the surface of which usually presents asperities of different kinds : the inner 

 membrane (endospore) of the spore forms, when the exospore has become ruptured 

 in germination, the first hypha (or more than one) from which the mycelium takes 

 its origin. 



The mycelium produces in many instances conidiophores upon which the 

 conidia are developed by abstriction. The conidia generally have a smooth surface 

 and a very thin external membrane. In many genera they do not occur, although 

 nearly-related genera possess them in abundance : for instance, they are absent in 

 Tuber and present in Penicillium, In addition to the conidiophores there occur 

 beside the fructification or even upon it, certain peculiar receptacles in which larger 

 or smaller conidia {Stylogonidia in Pycnidta, Spermatia in Sper?nogom'a) are developed, 

 which, ever since the publication of the important mycological works of Tulasne, 

 have been regarded as non-sexual reproductive cells of the Ascomycete upon which 

 they exist. Since De Bary has shown that in many cases the pycnidia belong to 

 other Fungi which are parasitic upon those in question, there has been some justifi- 

 cation for the assumption that the so-called spermogonia also represent distinct 

 genera of Fungi ; and this assumption gains in probability when it is considered that 

 it deprives the doctrine of the pleomorphism of Fungi of its last remaining support. 



(i) Gymnoascus ^ is one of the simplest of the Ascomycetes. It is a small Fungus 

 growing upon horse- or sheep-dung, the mycelium of which developes numerous sexual 

 organs. Here the poUinodium and the carpogonium are completely similar before 

 fertihsation, but after it has taken place the carpogonium divides so as to form a row 

 of cells which grow out into short branched filaments bearing at their ends dense 

 masses of asci each containing eight spores. As the investment is quite rudimentary 

 the fertile portion of the fructification is in this case naked, and resembles, in this 

 respect, that of the simplest Florideae. {Nemalion). 



(2) Discomycetes ^. In order to illustrate as fully as possible the formation of 



^ Baranetzky, Bot. Zeitg. 1872, no. 10. 



' De Bary, Ueber die Ffuchtentwickelung der Ascomyceten, Leipzig, 1863, p. 11. — De Bary 

 tind Woronin, Beitrage zur Morphologic u. Physiologie der Pilze, 2nd series, pp. i and 82, Frankfort 

 1866. — Tulasne, Annales des Sci. Nat. 5th series, vol. VI, p. 247. 1866. — Glinka- Janczewski, Bot. 

 Zeitg. 1871, no. 18, [Quart. Journ. Micr. Sci. 1878, p. 438. — Brefeld, Unters. lib. Schimmel- 

 pilze IV.] 



