CHAPTER V. — COMPARA TIVE REVIEW. — ASCOMYCETES. — COLLEMACEAE. 2 1 3 



The further development shows that the spirally coiled portion of the archicarp 

 is the ascogonium or place from which the formation of the asci proceeds, while 

 the elongated part with its point projecting above the surface of the thallus is the tricho- 

 gyne 1 , serving as the receptive-organ in fertilisation and conveying its influence to the 

 ascogonium. Both parts are divided as they grow by transverse walls into cylindrical 

 cells, of which there are about twelve in the ascogonium and as many or more in the 

 trichogyne ; they are all at first thin-walled and filled with a homogeneously hyaline 

 protoplasm. The formation of archicarps generally takes place under the same 

 external conditions as the discharge of the spermatia ; namely, in the cool, damp, 

 rainy period of the year. If the spermatia which have reached the surface of the 

 thallus encounter the top of a new-formed trichogyne they attach themselves firmly 

 to it often in great numbers, and notwithstanding the difficulty of minutely observing 

 such small bodies when adhering to the comparatively thick trichogyne, Stahl was 

 repeatedly able to assure himself that some of them put out a short process by means 

 of which their protoplasm becomes united with that of the apex of the trichogyne 

 (Fig. 101 D). The effect of this union with the spermatia is seen in peculiar 

 changes in the trichogyne, advancing from the apex to the base, and in the asco- 

 gonium and surrounding parts, and these changes are not observed if no union takes 

 place between trichogyne and spermatia. The changes are these ; the cells of the 

 trichogyne lose their turgidity and shrink into slender threads; their transverse 

 walls only maintain their former breadth and at the same time swell strongly in the 

 direction of the axis of the trichogyne, and thus form knot-like protuberances in the 

 collapsed cell-row. The cells of the ascogonium continue turgescent, thin-walled, and 

 rich in protoplasm, and increase in size and number by transverse divisions. Finally 

 a large number of branches begin to be formed in the neighbourhood of the ascogo- 

 nium on the adjacent hyphae of the thallus, and these ramifying repeatedly and inter- 

 twining grow round the outside of the ascogonium and also push in between the turns 

 of its spiral and force them apart ; the ascogonium is thus rapidly inclosed in a mass 

 of closely coiled filaments, the first-state of the envelope of the fructification. The coil 

 is at first round and occupies the place in the interior of the thallus in which the 

 ascogonium inclosed by it was first formed. When it has reached a certain size 

 (Fig. 102), the hyphae on the side towards the adjoining surface of the thallus send out 

 branches which again branch repeatedly, and the final ramifications are the first 

 paraphyses which grow straight towards the surface of the thallus, pushing aside the 

 tissue of the thallus which stands in their way, and terminate in it. At the same time 

 the envelope-coil which was originally round increases in breadth in the direction of 

 the surface of the thallus — chiefly no doubt by centrifugal formation of new hyphal 

 branches on its lateral margin, so that it assumes the form of a concave disk cutting 

 the surface of the thallus with its edges; and thus it developes into the ultimately 

 pseudoparenchymatous excipuhim, which continues for some time to increase in 

 breadth at the margin which rests on the surface of the thallus. As the development 

 of the excipulum advances, new paraphyses similar to the first shoot out one after 

 another from its side towards the surface of the thallus, pushing aside the tissue of 



1 The term was introduced by Bornet and Thuret to denote the analogous organs in the 

 Florideae. See Ann. d. sc. nat. ser. 5, VII, p. 137. 



