442 SYSTEMATIC BOTANY. 



a time ; but while an ordinary zoospore after a time germinates and forms 

 a new thallus, the androspores attach themselves to the sides of the female 

 spore or sporangium. 



In this situation they grow into a sort of prothallus ; the lower part 

 becomes dilated or pear-shaped, while the upper extremity develops one 

 or two small cells one over the other. These are the antheridia ; and in 

 each of them is formed a spermatozoid, the fecundating body. These 

 latter, when mature, are ciliated and butt against the top of the anthe- 

 ridium, and at length cause its detachment in the shape of a little lid. 

 In this manner they escape from the antheridium, move about for a time 

 in the water by means of their cilia, and ultimately pass into the female 

 spore through an opening previously specially prepared for its passage in 

 the summit of the female spore. Here the spermatozoid comes into con- 

 tact with a quantity of colourless granular mucilage formed in that situa- 

 tion prior to fecundation, the distention consequent on which seems to 

 account for the formation of the aperture through which the fecundating 

 body passes. The spermatozoid touches the mucilage, or even penetrates it 

 to some extent, and becomes blended with it, and thus fertilizes the spore, 

 which subsequently becomes invested by a cell-wall in the ordinary way. 



Vaucheria is a genus of filamentous Confer void Algae, in which the long 

 branched filament consists of a single enormously developed cell. This 



Fip;. 506. 



VaucJieria: A, A, spermatozoids ; B, C, horn-like antheridium ; D, D', sporanges; 

 E, spore. 



plant is commonly propagated by a peculiar kind of zoospore discharged 

 from the thickened end of the filament or of its branches. But at certain 

 epochs lateral structures are developed at the sides of the filaments, as 

 branch cells, which become shut off from the main tube by septa ; some 

 of these processes expand into ovate and beaked or bird's-head-shaped 

 bodies, others into short curled filaments or " horns." The former are 

 sporanges, the latter antheridia (fig. 506). When ripe, the antheridia or 

 "horns" discharge their cell-contents in the form of numerous spindle- 

 shaped corpuscles, moving actively by the help of a pair of cilia. Mean- 

 while an orifice is formed in the "beak of the sporange, and some of the 

 spermatozoids make their way in, so as to come into direct contact with 

 the cell-contents. This phenomenon is followed by the closing-up of the 

 sporange by a membrane, and the conversion of its contents into a fertile 

 restinc/-spore. 



Spliceroplea is another genus of filamentous Confervoids, composed of two 

 rows of cylindrical cells, in which fertilization of the resting-spores by 

 spermatozoids has been directly observed (Cohn). In some of its cells 



