3°<5 



PART IV. VEGETABLE TAXONOMY. 



monly the case, on separate plants of the same species. The 

 antheridia occur either singly or in groups at the ends of certain 

 branches, and the antherozoids are minute rounded, non-ciliated 

 and non-motile particles, and are dependent therefore on water- 

 currents or on animalculae for their conveyance to the carpo- 

 gonia. The latter are more complex organs than the oogonia of 

 other algae. In the course of their development, the unicellular 

 or multicellular mass first formed becomes differentiated into 

 two portions, an upper portion, called the trichogyne, usually a 

 straight, hair-like process, and an enlarged basal portion. 



Fig. 506. 



Fig. 507. 



Fig. 506. — Lejolisia mediterranea, one of the Red Marine Algae ; portion of filament, 

 showing asexual reproduction by tetraspores. a, represents tetrasporangium. Three of 

 the four spores are shown in the figure, the other is concealed behind them. 



Fig. 507. — Lejolisia mediterranea : portion of fertile filament, showing mode of sexual 

 reproduction, a, antheridiutn nearly ripe ; b, ripe antheridium with escaping antherozoids ; 



c, carpogonium, bearing at its apex a trichogyne, to which two antherozoids are attached ; 



d, nearly ripe carpogonium, showing carpospores in its interior ; e, ripe carpogonium dis- 

 charging one of its carpospores, /. Magnified about 150 diameters. 



The part which receives the fertilizing influence of the anther- 

 ozoids is the trichogyne, but this does not undergo development 

 in consequence, but communicates the influence to the basal 

 portion, and then soon withers away, while the latter undergoes 

 very considerable changes. These differ considerably in differ- 

 ent species, but in all, the fertilization stimulates a considerable 

 vegetative growth, which results in the production of spores, 



