VIII 



MARATTIALES 



277 



closely that of Angioptcris, than that of Marattia. The rhizoids 

 are multicellular, recalling those of the gametophyte of 

 Botrychinm. 



The very old prothallia sometimes branch dichotomously 

 (Fig. 151, B, C), and the process is identical with that in the 

 thallose Hepaticse. The two growing points are separated by 

 a median lobe in the same way, and the midrib with the sexual 



k ■■''->"IV 



r- 



Fig. 151. — Marattia Douglasii. A, Prothallium about one year old, X2; B, the same 

 prothallium about a year later, showing a dichotomy of the growing point; C, the 

 same seen from below, showing two archegonial cushions (^) ; D, prothallium with 

 young sporophyte, X4; E, a somewhat older one, seen from the side; r, the pri- 

 mary root. 



organs upon it forks with It, exactly as we find, for example, 

 the antheridial receptacle forking in Fimbriaria Californica 

 (Fig. I, A). Besides this form of branching, w^hich is not 

 common, adventitious buds are produced upon the margin of 

 the thallus very frequently. These grow in precisely the same 

 way as the main prothallium, and after a time may become 



