ASCOBOLVS — SPIROGYRA. 



737 



by means of their further growth eventually produce the spores, and, usually, also 

 an investment around them. Here, however, it is to be mentioned that in the 

 Florideae the fertilisation is accomplished not by pollinodia, as in the Ascomycetes 

 considered above, but by means of very small cells which are developed in large 

 numbers in special male organs ; these cells are set free and passively carried by the 

 water, and then, coming itito the neighbourhood of the trichogyne referred to, fix them- 

 selves on to it, and empty their contents into it. Stahl has shown that the fruct ificatiog 

 of many Lichens also is accom pli shed in a. very^ similarwaY^ 



Although their external appearance is extremely different, the Mucorini never- 



Fig. 410. — Spirogyya longata. To the left several cells of two filaments which are about to conju^te. They show 

 the spiral chlorophyll-bands, in which crown-hke arrangements of starch-grains are lying, as well as small drops of oil. 

 The nucleus of each cell is surrounded by protoplasm, from which threads go to the ceU-wall. b preparatory to conjugation. 

 A, to the right, cells engaged in conjugation. The protoplasm of the one cell is just passing over into the other at a \ 

 in b the two protoplasmic masses have already united. In B the young zygotes are clothed with a wall. 



theless agree essentially with the Conjugatse — a subdivision of Algae — in so far as 

 in the latter also cells externally alike in nature, and especially equal in size, combine 

 with one another and allow their protoplasmic contents to fuse into a single mass, which 

 then forms a resting zygote and only becomes capable of germination in the following 

 year. Of this process, which of course presents numerous modifications again in the 

 various species of Conjugatse, Fig. 410 will serve to elucidate the most important 

 points. Fig. 410 represents, to the left, short portions of two long filaments of 

 Spirogyra, found everywhere in May and June, as matted green masses floating 

 on still water. These two filaments have (within the dense mass of the Alga) 

 become laid parallel to one another for some distance, whereupon, in each case 



