128 THE PHENOMENON OF 



which becomes torn at the side or bottom.* The con- 

 trast in the development of the upper and lower ends 

 of the cell presents itself still more strikingly in Botry- 

 dium. The young plant is a globular cell, which might 

 be readily mistaken for a Protococcus, but, with further 

 development, a hyaline prolongation is produced below, 

 penetrating into the earth and branching like a root, 

 while the upper part of the cell swells up more and more 

 into a large obovate vesicle. The mucilaginous contents 

 form a lining to the walls, containing numerous chloro- 

 phyll vesicles. After the growth is complete, numerous 

 germ-cells are formed out of the lining coat of the wall, 

 and these do not appear to swarm, but are set free by the 

 membrane of the parent- cell becoming gelatinously 

 softened, collapsing, and finally dissolving. In Vauclieria 

 the lower part of the cell grows out in like manner into 

 a branched pale-coloured root, and the upper part is 

 elongated in a still more considerable degree into a 

 stem-like filament, which grows on and on by apical 

 development until its growth is finally arrested by fruc- 

 tification. From the ascending filament arise lateral 

 prolapsing branches, endowed with special faculty of 

 apical growth, some of these being large and erect like the 

 main stem, others small and divergent. A single moving 

 germ-cell is produced in the point of each erect branch ; 



* Ascidium acuminatum, A. Br., occurs near Freiburg, in waterbuts or 

 troughs, or on stones or confervse in rills flowing from springs. It resembles 

 in aspect Characium Sieboldii, A. Br., occurring in similar situations, from 

 which it is easily distinguished by the more bulging form of the cell, more 

 apiculated at the apex, and never containing more than one starch-vesicle. 

 The swarming germ-cells are j^th T ^ th of a millim. long, longish, and 

 furnished with two cilia at the narrower end, 1^ to 2 times as long as the 

 germ-cell. After the germ-cell has settled down by the ciliated end, the 

 plant grows rapidly, is at first slender and attenuated upwards and down- 

 wards; subsequently it becomes bellied out, almost ovate, running out 

 suddenly into a sharp point above. The full-grown cell is about 55 millim. 

 long. While young, the cell is filled up uniformly with green contents, 

 later they form a rather thick coat over the wall, uneven on the inner i'ree 

 surface. When the formation of germ-cells commences the starch-vesicle 

 disappears, and the coat lining the wall becomes subdivided into 50 GO 

 gonidia. 



