EEPRODUCTION OF CRTPTOGAJnA. 751 



sporecE, and probably occurs also in the Ehodosporeae. There 

 appear to be two modes in which such fecundation occurs in the 

 above ; thus, in the Volvocinea, and in certain Chlorosporea^, 

 the fecundation takes place before the spore has separated from 

 its parent ; and in the Melanosporeae, after both the spore and 

 ciliated spermatozoids have been discharged. 



As an illustration of the first mode of fecundation we may take 

 Vaucheria. It is thus described by Henfrey : — " This plant is com- 

 monly propagated by a peculiar kind of zoospore {fig. 830, g), 

 discharged from the thickened end of the filament or its branches. 

 But at certain epochs lateral structures are developed at the sides 

 of the filaments, as branch-cells, which become shut ofi' 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 sporangia, the 

 latter antheridia. When ripe, the antheridia or ' horns ' dis- 

 charge their cell-contents in the form of numerous spindle- 

 shaped corpuscles, moving actively by the help of a pair of 

 cilia. Meanwhile an orifice is formed in the beak of the 

 sporangium, and some of the spermatozoids make their way in, so 

 as to come into direct contact with the cell-contents. This phe- 

 nomenon is followed by the closing up of the sporangium by a 

 membrane, and the conversion of its contents into a fertile 

 resting spore.'' This process is subject to various modifications 

 in the other genera in which it occurs. 



The second mode of fecundation of naked spores by ciliated 

 spermatozoids, occurs in the Melanosporese, and has been especially 

 investigated by Thuret, His observations have been thus con- 

 densed by Henfrey: — "In this order the conceptacles (fig. 837) 

 produce in their interior, bodies of two kinds, antheridia (figs. 

 838, and 839, a, a, a) and spore-sacs (fig. 837, sp), either toge- 

 ther or in separate conceptacles (monoecious), or in separate 

 plants. The antheridia discharge 2-ciliated spermatozoids (fig. 

 838), which are poured out through the pores of the receptacles 

 (fig. 153, t) into the surrounding water. At the same time 

 the spore-sac (fig. 837, sp) bursts, and emits an inner sac, 

 in which may be observed 2, 4, or 8 spherical corpuscles, des- 

 titute of a cellulose membrane ; this inner sac breaking loose, 

 bursts and discharges its corpuscles, which, like the spermatozoids, 

 pass through the pores of the receptacle into the water. Here 

 they become surrounded by a cloud of spermatozoids which 

 attach themselves to the surface, and by their ciliary movement 

 cause the spores to revolve. In the course of a few minutes 

 usually, a cellulose membrane is formed upon the surface of the 

 globular corpuscle (by secretion from its primordial utricle ? ) 

 and it becomes a cell, which subsequently germinates, gro wing- 

 by cell- division into a new frond." 



B, Beproduction of Acrogens. — Of the sexual nature of the 

 3c 



