THE CiREAT (iROUPS OF ALd/E 



259 



and reddish-brown) making tliem very attractive. They 

 show the greatest variety of forms, branching fihiments, 

 ribbons, and fihiiy phites prevailing, sometimes branching 

 very profusely and delicately, and resembling m.osses of 

 fine texture (Figs. 222, 223, 224, 225, 32G). The diiferen- 

 tiatioii of the thallus into root and stem and leaf-like struc- 

 tures is also common, as in the Brown Algfe. 



174. Eeproduction. — Eed Algaj are very peculiar in both 

 their asexual and sexual reproduction. A sjjorangiuni pro- 

 duces just four asexual spores, but they have no cilia and 

 no power of motion. They 

 can not be called zoospores, ^Qi" 



therefore, and as each spo- a 



Fig. 2"27. A red alga (Cfd/tf/wnunn/i), show- 

 ing sporangium (A), and tlio tctraspoi-fs 

 discliarged (5).— After Thuret. 



Fill. 828. A rod alga (Nemri!kw) ; A, 

 sfKtial braiiolics, showing antheri- 

 dia (a), oogoninm (o) with its trich- 

 ogyne ((}, to which arc attached two 

 spcrniatia (,s'} ; B, beginning ot a 

 cystocarp (o), the trichogyne (0 f^till 

 showing ; 0. an almost mature cys- 

 tocarp (o), with the disorganizing 

 trichogyne (/I.— After Knt. 



rangium always produces just 

 four, they have been called 

 ietraspore.s (Fig. 227). 



Ked Algffi are also heterog- 

 amous, but the sexual process has been so much and so 

 variously modified that it is very poorly understood. The 

 antheridia (Fig. 228, A, ti) develop sperms which, like the 

 tetraspores, have no cilia and no power of motion. To dis- 



