CRYPTOGAMS 



375 



The asexual SPOKES are noil-motile ; they have no cilia and are simply naked, 

 spherical cells. They are produced, usually, in groups of four, by the division 

 of a mother cell or sporangium, from which they are in time set free by the 

 transverse rupture of its walls. The spor- 

 angia themselves are nearly spherical or 

 oval bodies seated on the thalloid filaments 

 or embedded in the thallus. The spores 

 escape by a transverse rupture of the wall 

 of the sporangium. ' In consequence of 

 their usual formation in fours, the spores 

 of the Florideae are termed TETRASPORES 

 (Fig. 312). They are analogous to the 

 swarm-spores of other Algae ; similar spores 

 are found also in the Dictyotaceae among 

 the brown Algae. 



In the construction of the sexual 

 organs, particularly the female, the Rhodo- 

 phyceae differ widely from the other Algae. 

 Hatrachospermum moniliforme, a fresh- 

 water form, may serve as an example to 

 illustrate the mode of their formation. This 

 Alga possesses a brownish thallus, en- 

 veloped in mucilage, and consisting of verticillately branched filaments. 



FIG. 312. Callithamnionwrymbosii.ni. .4, Closed 

 sporangium ; I), empty sporangium with 

 four extruded tetraspores. (After THTTRF.T. ) 



The 



FIG. 313. Batrachospermum iiwniliformc. A, Male branch with antheridia, isolated 1>\ pressure ; 

 s*, a spermatium ; s, a .spermatium escaping from an antheridum ; r, an empty antheridium. 

 J5, female branch wjtli an unfertilised carpogonium ; c, basal portion ; t, trichogyne of carjK)- 

 gonium. C, female branch with fertilised carpogonium ; s, the spermatium after the fusion of 

 its contents with the trichogyne ; c, fertile filaments developing from the basal portion of the 

 carpogonium. (x 540.) 



sexual organs appear in the autumn and form on the branching whorls glomeruli 

 or spherical bodies composed of short, radiating branches. 



The antheridia, also known as spermatangia (Fig. 313 A), are produced, usually 

 in pairs, at the ends of the radiating branches of a glomerulus. Each antlu-ridium 



2 B 2 



