REPKODUCTION OF CH.ETO PHOR ACEJE. 



321 



200. The ChcetopJioracece constitute another beautiful and in- 



id plants, of which some species 

 found in fresh and pure water, 



teresting little group of Confervoid plants, of which some species 

 inhabit the sea, whilst others are fou: 



FIG. 109. 



rather in that of gently mov- 

 ing streams, however, than in 

 strongly flowing currents. Ge- 

 nerally speaking, their filaments 

 put forth lateral branches, and 

 extend themselves into arbo- 

 rescent fronds ; and one of the 

 distinctive characters of the 

 group is afforded by the fact, 

 that the extremities of these 

 branches are usually prolonged 

 into bristle-shaped processes 

 (Fig. 109). As in many pre- 

 ceding cases, these plants mul- 

 tiply themselves by the con- 

 version of the endochrome of 

 certain of their cells into "zoo- 

 spores;" and these, when set 

 free, are seen to be furnished 

 with four large cilia. " Rest- 

 ing-spores" have also been 

 seen in many species ; and it is 

 probable that these, as in Con- 

 fervaceee, are true generative 

 products of the fertilization of 

 the contents of "germ-cells" by " antherozoids" developed 

 within " sperm-cells" ( 198). Nearly allied to the preceding 

 are the Batrachospermece, whose name is indicative of the strong 

 resemblance which their beaded filaments bear to frog-spawn ; 

 these exhibit a somewhat greater complexity of structure, and 

 afford objects of extreme beauty to the Microscopist. The 

 plants of this family are all inhabitants of fresh water, and they 

 are chiefly found in that which is pure and gently flowing. 

 "They are so extremely flexible," says Dr. Hassall, "that they 

 obey the slightest motion of the fluid which surrounds them ; 

 and nothing can surpass the ease and grace of their movements. 



into sperm-cells and germ-cells is manifested in Zygnema, by the passage of the whole 

 endochrome of those of one filament into the cavities of the other, and by the formation 

 of the spores within the latter. In Spirogyra, moreover, the endochrome of one set of 

 cells becomes converted into antherozoids before conjugation, whilst that of the other 

 aggregates into a sporangial mass; thus exhibiting the second stage of differentiation. 

 Further, there are certain species which agree with the ordinary Conjugates in their 

 general habit, and which form " resting-spores" like theirs, but in which no conjugation 

 has been observed; and it seems not improbable that in these, as in Sphseroplea, the 

 antherozoids make their way out of the sperm-cell by minute apertures in its wall, and 

 swim freely about before finding their way into the germ-cell through the apertures in 

 its wall; still, however, performing by this means the very same act, as that which is 

 accomplished by the more direct process of conjugation, viz., the introduction of the 

 contents of the sperm cell into the interior of the germ-cell. 



21 



Branches of ChcetopJtora elegans. in the act 

 of discharging ciliated zoospores, which 

 are seen, as in motion, on the right. 



