44 



PLANT STRUCTUEES 



tinguish them from the ciliated sperms, or spermatozoids, 

 which have the power of locomotion, these motionless male 

 gametes of the Ked Algae are usually called spermatid 

 (singular, spermatium) (Fig. 28, A, s). 



The oogonium is very pe- 

 culiar, being differentiated 

 into two regions, a bulbous 

 base and a hair-like process 

 (trichogyne), the whole struc- 

 ture resembling a flask with a 

 long, narrow neck, excepting 

 that it is closed (Fig. 28, A, 

 o, t). Within the bulbous part 

 fertilization usually takes 

 place ; a spermatium attaches 

 itself to the trichogyne (Fig. 

 28, A, s)\ at the point of 

 contact the two walls become 

 perforated, and the contents 

 of the spermatium thus enter 

 the trichogyne, and so reach 

 the bulbous base of the oogo- 

 nium. The above account rep- 

 resents the very simplest con- 

 ditions of the process of fer- 

 tilization in this group, and 

 gives no idea of the great and 

 puzzling complexity exhibited 

 by the majority of forms. 



After fertilization the trich- 

 ogyne wilts, and the bulbous 

 base in one way or another 

 develops a conspicuous struc- 

 ture called the cystocarp (Figs. 28, 29), which is a case con- 

 taining asexual spores ; in other words, a spore case, or kind 

 of sporangium. In the life history of a red alga, there- 



Fig- 29. A branch of Polytiphonia 

 ons of the red algae, showing the 

 rows of cells composing the body 

 (A), small branches or hairs (B). 

 and a cystocarp (C) with escaping 

 spores (D) which have no cilia (car- 

 pospores). — Caldwell. 



