i6 



LECTURE XLI. 



<k 



In Piplocephdiis, as in all JMucorini or Zygomycetes, the result of the fertilisation 

 is thus a single large cell capable of development (the zygospore or zygote). IMatters 

 are strikingly different in the case oi Ascoholus, an Ascomycetous Fungus studied in 

 detail by Janczewski, as shown diagrammatically in Fig. 409. Here also m in are 

 certain of the ramifications of the richly branched mycelium. The end of a 

 branch c becomes filled with protoplasm, swells up considerably, and undergoes 

 several transverse divisions; a neighbouring filament then applies itself closely to 

 the anterior cells of the carpogonium c by means of its thin branches /. This organ 

 has been named the poUinodium. Whether a direct fusion of its protoplasmic 

 contents with those of the carpogonium results, or whether a soluble fertilising 

 substance passes over from it, is not known ; but analogy with all other known 

 processes of fertilisation scarcely permits a doubt that one or the other occurs, and 

 that we here ha\e an actual process of fertilisation. Its effect, however, is here quite 

 ^ different from that in the previous case. 



The result is not one resting cell capable 

 of germination, but, stimulated by the 

 fertilisation, a fruit-body or fructification is 

 developed which is very voluminous and 

 highly organised in comparison with the 

 mycelium. This body in its turn consists 

 of two essentially different parts : from 

 one cell of the carpogonium (i. e. from 

 the female cell) a large number of 

 segmented fungus-hypha; .s-j grow forth, 

 on which the sporogenous asci a at 

 length arise in great numbers, as terminal 

 branches. Long before this spore-forma- 

 tion is accomplished, however, the mycelial 

 branches in close proximity to the ferti- 

 lising apparatus have also been stimulated 

 to renewed, vigorous, and entirely altered 

 growth ; they envelope the fertilising ap- 

 paratus, together with the ascogenous filaments s s, with a parenchymatous investing 

 layer//», rr, within which also the spore-forming asci a arise. Between the latter 

 are noticed thin barren hyphse, the so-called paraphyses, which originate from the 

 envelope. Finally, it hardly needs mention that the spores produced in the asci a, 

 when they germinate on a proper substratum, again give rise to a new mycelium, 

 on which, so to speak as a second generation in the above sense, the fructification 

 arises in consequence of the sexual act of fertilisation. 



In AscohoJus, as shown in Fig. 409, the cell which is fertilised, i. e. directly 

 touched by the pollinodium, is not the one which eventually gives rise to the asco- 

 genous filaments s, and the sporogenous asci on these. The case is exactly similar 

 in that great subdivision of the Algae, the Florideae, where the female sexual organ 

 likewise consists of a multicellular body, from which si)rings a single cell, the 

 trichogyne, in the form of a long filament, which takes up the male fertilising 

 substance; thus in the Floridece also it is other cells of the carpogonium which 



Fig. 409. — Diajjrani of a transverse sect 

 fructification of Ascobolus /iir/iii-acein, an A 

 Janczevvski's figures), »t mycelium ; c carpogoniu 

 linodium ; s ascogenous hyphn; ; a asci ; rp steril 

 the fructification, from which the paraphyses A ate ( 



ycete (from 



'ssue of 

 eloped. 



