312 



THALLOPHVTES. 



become multicellular in consequence of the formation of transverse septa within them, 

 and, lying closely side by side, they give rise to a pseudo-parenchyma. From the 

 internal surface of this investment, as it increases in size, short filaments are given 

 off which fill up the space between it and the carpogonium which has not as yet 

 undergone much change (V h). The still unicellular carpogonium now begins to 

 grow vigorously; it is divided by a transverse septum into two cells, an upper and 

 a lower, and may be regarded as a simple form of ascogenous filament, the apical 

 cell of which is directly converted into an ascus (V a). The apical cell, by its rapid 

 growth, soon occupies the whole of the cavity of the fructification, and eight spores 

 are produced by free-cell-formation in its protoplasm. Slight pressure upon the fruit 

 causes the extrusion of the ascus (II a). In other Erysipheae, the perithecia of 

 which contain several asci, as E. Umbelliferarum, communis^ lamprocarpa^ etc., the car- 

 pogonium is also originally unicellular, but it grows within the investment into a long, 

 thick, curved filament, which is divided into segments by numerous septa. Many of 

 these segments throw out lateral branches which bear the asci. 



Fig. 207. — / Conidiophore ; //ripe perithecium oi Erysiphe (Spfuerotheca) pa7t7iosa (after Tulasne); ///carpo- 

 gonium and pollinodium ; IV the same after fertilisation ; V the young perithecium of Podosphara, Castagnei (after ' 

 De Bary) ; c carpogonium ; p pollinodium ; h wall of the perithecium ; a the single ascus. 



These Erysipheae which have numerous asci afford a transition to the EurotiesB^ in 

 which the carpogonium, even before fertilisation, elongates considerably and becomes 

 spirally wound. 



The life-history of Eurotium repens and that of Eurotium Aspergillus glaucus have 

 been also recounted in detail by De Bary. Both species are found on the most 

 various decaying or dead organic bodies, and are especially abundant on preserved fruit. 

 The Fungus makes its appearance as a delicate flocculent white mycehum overspreading 

 the surface, from which the upright conidiophores soon rise in large numbers. These 

 swell in the upper part into a globular form, and on the upper half of the globe 

 there arise a number of peg-shaped projections, densely crowded and arranged radially, 

 the sterigmata, each of which produces gradually a long chain of greenish conidia ; 

 so that finally the head of the receptacle is covered by a thick layer of them. During 

 this formation of conidia, the sexual organs appear on the same mycelium. The female 

 organ, the carpogonium, is the corkscrew-like end of a branch of the mycelium (Fig. 208, 

 A, as), the coils of which become gradually closer, until, when actually in contact, they 

 form a hollow spiral {B, C). During this process about as many septa are formed as 

 there are turns of the helix (i.e. 5 or 6). From the lowest coil of the carpogonium two 



* [Wilhelm, Die Pilzgattung Aspergillus, 1877.] 



