IV. 



THE ANTHOCEROTES 



145 



rhizoids, and a little later the first dichotomy of the growing 

 point takes place. Up to this time the young plants appeared 

 entirely free from Nostoc, but soon after they were found to 

 be infected, which no doubt was connected with the formation 

 of the mucilage slits through which the Nostoc enters the 

 thallus. 



In several species of Anthoccros, especially those inhabiting 

 regions with a marked dry season, tubers are developed by 

 means of which the plants are perennial. Howe (3) finds such 

 tubers developed in A. phymatodes, of California, and they are 

 found in A. dichotomus^ of Southern Europe, and in A. tuher- 



sp 



Fig. 77. — Anthoceros fusiformis. A, Young plant showing the first rhizoid (r) ; B, 

 upper part of an older one with the first mucilage cleft ist) ; x, the growing 

 point, X215. 



osus of Australia (see also GoebeL (22), p. 293). The struc- 

 ture of these tubers has been studied by Ashworth (i), in 

 A. tuherosus. 



Dendroccros 



Dcndroceros includes about a dozen species of tropical Liv- 

 erworts, which are distinguished at once from Anthoccros by 

 the very characteristic form of the thallus. This has a massive 

 midrib, projecting below\ but the rest of the thallus is but one 

 cell thick and forms lateral wings wdiich are much folded and 

 lobed, so that the aspect of the plant is somewhat like a Fossom- 

 bronia. As in Anthoceros, some species have a perfectly com- 

 10 



