376 



BOTANY 



PAKT 11 



sequence of their visual formation in fours, the spores of the Floiideae are termed 

 TETRASPOIIES (Fig. 302). They are analogous to the swarm-spores of other Algae ; 



similar spores are found also in the Dict3'0- 

 taceae among the browu Algae. 



In the construction of the sexual 

 organs, particularly the female, the Rhodo- 

 phyceae differ widely from the other Algae. 

 Batrachos'jKrmum Tno'iiiliforme, a fresh- 

 water form, may serve as an example to 

 illustrate the mode of their formation. 

 This Alga possesses a brownish thallus, 

 enveloped in mucilage, and consisting of 

 verticillately branched filaments. The 

 sexual organs appear in the autumn on the 

 branching whorls seated on closely crowded, 

 short, radiating branches. 



The antheridia, also known as sperma- 

 tangia (Fig. 303, A), are produced, usually 

 in pairs, at the ends of the radiating 

 lu'anches. Each antheridiura consists of 

 a single thin- walled cell, in which the 

 whole of the protoplasm, as is the rule in all Khodophyceae, is consumed 

 in the formation of one uninucleate .spermatium ; according to some authors 



Fiii. 312. — Callithamnioncorymhosum. A, Closed 

 sporansjium ; B, eiripty sporangium with 

 four extrudeil tetraspores. (Aft^r Thuret.) 



Fio. Sl)3. —liatrarlinspprmum mnnili forme. A, Male branch with antheridia, isolated l)y pressure ; 

 B*, a spermatiiun ; .■!, a spermatium escapiiis from an anlheridiuni ; v, an empty antlieridium. 

 li, female branch witli an nnfertilise.d carpogonium ; r, basal portion ; t, tricliogyne nf carpo- 

 gonium. C, femalt^ branch with fertilised carijogonium ; s, the spermatium after the fusion of 

 its contents with the triehogyne ; c, fertile lilaments developing from the ba.sal portion of the 

 carpogonium. (x .'i40.) 



the nucleus of the si)ermatinm divides into two. The spermatia are nearly 

 s[)herical, and are invested with a thin outer membrane or cell wall. They 

 are non- motile, unlike the ciliated .spermatozoids of the other Algae, and 

 have therefore received a distinctive name. In consequence of their incajtacity 



