EUPHYCOPHYTA 229 



row of large cells. Numerous branches of limited growth arise in 

 whorls from the nodes and often bear long hairs at the ends. The 

 basal cell of such a branch can give rise to a branch of unlimited 

 growth or else to corticating cells that grow downward and invest 

 the main axis. The cells of the thallus are uninucleate and contain 

 only one pyrenoid. Reproduction takes place by means of mono- 

 spores (though these are restricted to the juvenile phase), carpo- 

 gonia and antheridia. The last-named arise as small, round, 

 colourless cells at the apices of short, clustered, lateral branches. 

 The carpogonia are also terminal and possess a non-nucleate tri- 

 chogyne, separated by a constriction from the rest of the organ. 

 The trichogyne shrivels away after fertihzation. The nucleus of the 

 zygote divides twice, giving rise to four nuclei; these pass into 

 protuberances that form from the carpogonium and branch to give 

 a mass of gonimoblast filaments. Each branch terminates in a 

 sporangium that produces a single naked carpospore. This secretes 

 a wall soon after liberation. On germination this gives rise to a 

 microscopic branched filamentous stage, which, on account of 

 earlier confusions is now known as the 'Chantransia' stage. Prac- 

 tically all fresh-water species of Chantransia represent a phase in 

 the Hfe cycle of a species of Batrachospermum. The *Chantransia' 

 phase can reproduce itself indefinitely, but eventually a new adult 

 Batrachospermum plant arises as a vegetative lateral branch of the 

 'Chantransia' filament. The 'Chantransia' stage corresponds to the 

 *Conchocelis' phase in Porphyra and both represent the prostrate 

 portion of the heterotrichous thallus. 



The fresh-water Lemanea (Lemaniaceae) has a more compact, 

 pseudo-parenchymatous thallus and much the same kind of 

 structure is found in the marine Naccariaceae. The carpogonial 

 branches are borne on special, Httle short shoots. The fertilized 

 nucleus passes from the carpogonium into the hypogenous cell 

 below and a wall of vegetative cells is formed around the gonimo- 

 blasts. 



^o^^^MAiso^ikCEhE: Asparagopsis (like asparagus fern). Fig. 126 



The erect shoots arise from a perennial creeping thallus. This 

 prostrate thallus possesses vesicular or iodine-containing cells and 

 modified branches act as attachment organs. In the erect thallus 

 primary and secondary laterals form a cortex which is often 

 separated from the original axis by a space. In all Bonnemaison- 



