J 58 THALLOPHYTES. 



closer, until, when actually in contact, they form a hollow spiral {B, C). During this 

 process about as many thin septa are formed as there are turns of the helix (/. e. 5 or 6). 

 From the lowest coil of the ascogonium two slender branches now shoot out at opposite 

 places, which grow upwards on the outside of the helix ; one of these developes more 

 quickly, reaches the uppermost coil, and becomes closely attached to it by its apex {B,p). 

 This branch is the Antheridium (Pollinodium of De Bary). Conjugation takes place 

 between its apex and the ascogonium, the cell-wall being absorbed at the point of 

 contact, and the protoplasmic contents of the ascogonium and of the antheridium com- 

 mingling. Soon afterwards new filaments sprout out from the lower part of the 

 antheridium, as well as from the other branch, which increase in number, cling closely 

 to the spiral (C), and finally entirely envelope it. From these filaments a layer of 

 polygonal cells, the Perithecium {D}, is formed by numerous transverse divisions, en- 

 veloping the ascogonium. The cells of the enveloping layer grow inwards as papillae 

 which become septate (E). While the enveloping layer is increasing in size, the cavity, 

 which is thus enlarged, is filled up by the papillae, which finally insert themselves between 

 the coils of the ascogonium which have now become looser. These papillae thus become 

 divided by septa into numerous cells of similar diameter, so that at last the space 

 between the enveloping layer and the coils of the ascogonium is filled by a pseudo- 

 parenchyma (F). During these processes a larger number of septa arise in the asco- 

 gonium, and soon there shoot from its cells numerous commencements of branches, 

 which penetrate on all sides between the cells of the pseudo-parenchyma, become 

 septate, and ramify. Their last ramifications are the Asci (G), which therefore owe 

 their origin to the fertilised ascogonium. These internal changes are accompanied by 

 a considerable increase in size of the whole perithecium. During the development of 

 the asci, the pseudo-parenchyma becomes looser, its cells round themselves ofl', become 

 capable of swelling, lose their fatty contents, and finally disappear ; in the ripe peri- 

 thecium it is replaced by the asci. The increase in size of the cells of the parietal layer 

 keeps pace with that of the perithecium ; and they become covered with a sulphur- 

 yellow coating which attains a considerable thickness and consists probably of a resinous 

 or fatty substance. Finally the cells of the parietal layer collapse and dry up; the 

 eight-spored asci also dissolve, till finally the perithecium consists only of the brittle 

 yellow coating and of the mass of spores enclosed by it, which are set free by gentle 

 pressure. In a similar manner to the perithecium, the mycelium also becomes covered 

 by a coating, in this case chestnut colour, on which the perithecia are now individually 

 visible to the naked eye as yellow granules. The ripe spores (^Ascospores^ have the 

 form of biconvex lenses {H) ; when germinating the endospore which puts out the 

 germinating filament s\vells up violently and splits the exospore into two halves. The 

 mycelium which proceeds from the ascospores produces, like that which arises from 

 the conidia, at first conidia-bearing hyphae and afterwards perithecia ; but a proper alter- 

 nation of generations between sexual and asexual generations does not occur here^. 



For the different modes of origin of the perithecium in the Erysiphae, Sphaeriae, and 

 Sordariae, I must refer to the treatises of Woronin and De Bary already mentioned, 

 and now turn to the description of another pyrenomycetous Fungus the development 

 and structure of which is much more complicated, 'viz. Cla-viceps purpurea -, the Fungus 

 which produces Ergot. Its development begins with the formation of a filamentous 

 mycelium, which attaches itself to the surface of the ovary of Grasses, especially of rye, 

 while still enclosed between the pales, covers it with a thick weft, and partially pene- 

 trates into its tissue, while the apex and often other parts of the ovary remain exempt 



^ [Brefeld appears to have obtained the perithecia of Penicillium. Bot. Zeitg. Apr. 5, 1872. 

 -Ed.] 



2 Tulasne, Annales des Sci. Nat. vol. XX. p. 5. — Kiihn's Mittheilungen des landw. Inst, in Halle, 

 vol I. 1863. 



