GROWTH AND SEXUAL GEKESIS. 429 



f»getlier of the opposite halves of the endochrome info a 

 ball. Mostly, however, sporangia are products of conjuga- 

 tion. The endochromes of two cells unite to form the germ- 

 mass ; and these conjugating cells may be either entirely 

 independent, as in many JDesmtdiacece and in the Palmellm ; or 

 they may be two of the adjacent cells forming a thread, as in 

 some ConjuyatecB ; or they may be cells belonging to adjacent 

 threads, as in Zygnema. But whether it is originated by a 

 single parent-cell, or by two parent-cells, the sporangium, 

 after remaining quiescent until there recur the fit conditions 

 for growth, breaks up into a multitude of spores, each of which 

 produces an individual that multiplies asexually ; and the fact 

 here to be noted is, that as the entire contents of the parent- 

 cells unite to form the sporangium, their individualities are lost 

 in the germs of a new generation. In these minute simple 

 types, sexual propagation just as completely sacrifices the life 

 of the parent or parents, as does that form of asexual propa- 

 gation in which the endochrome resolves itself directly into 

 zoospores. And in the one case as in the other, this sacrifice 

 is the concomitant of a prodigious fertilitj'. Slightly 



in advance of this, but still showing us an almost equal loss 

 of parental life in the lives of offspring, is the process seen in 

 such unicellular Alg(B as Sydroga&trum, and in minute Fungi 

 of the same degree of composition. These exhibit a relatively- 

 enormous development of the spore-producing part, and an 

 almost entire absorption of the parental substance into it. 

 As evidence of the resulting powers of multiplication, we 

 have but to remember that the spread of mould over stale 

 food, the rapid destruction of crops by mildew, and other 

 kindred occurrences, are made possible by the incalculably 

 numerous spores thus generated and universally dispersed. 



Plants a degree higher in composition, supply a parallel 

 series of illustrations. We have among the larger Fungi, in 

 which the reproductive apparatus is relatively so enormous as 

 to constitute the ostensible plant, a similar subordination of 

 the individual to the race, and a similarly- immense fertility. 



