38 



PLANT STRUCTURES 



The other group, represented by Fucus (Fig. 21), pro- 

 duces no asexual spores, but is heterogamous. A single 

 oogonium usually forms eight eggs (Fig. 21, A), which are 

 discharged and float freely in the water (Fig. 21, E). The 

 antheridia (Fig. 21, G) produce numerous minute laterally 

 biciliate sperms, which are discharged (Fig. 21, G), swim in 

 great numbers about the large eggs (Fig. 21, F, H), and 

 finally one fuses with an egg, and an oospore is formed. 

 As the sperms swarm very actively about the egg and 

 impinge against it they often set it rotating. Both an- 

 theridia and oogonia are formed in cavities of the thallus. 



4. Ehodophyce^ (Red Algm) 

 31. General characters. — On account of their red colora- 

 tion these forms are often called Floridece. They are mostly 



marine forms, and are 

 anchored by holdfasts 

 of various kinds. They 

 belong to the deepest 

 waters in which Algae 

 grow, and it is probable 

 that the red coloring 

 matter which character- 

 izes them is associated 

 with the depth at which 

 they live. The Eed 

 Algae are also a high- 

 ly specialized line, and 

 will be mentioned very 

 briefly. 



32. The plant body. 

 — The Red Alga?, in 

 general, are more deli- 

 cate than the Brown 

 Algae, or kelps, their graceful forms, delicate texture, and 

 brightly tinted bodies (shades of red, violet, dark purple, 



Fig. 22. A red alga (Gigartina), showing 

 branching habit, and "fruit bodies."— 

 After Schenck. 



