290 



EVANS. 



Marginal gemmae occur abundantly on some of the plants collected 

 flby Neger but are apparently absent from all the other specimens. The 

 •gemmiparous branches are essentially like the others and present no 

 evidence of limitation in growth. The gemmae are usually scattered, 

 although a crowded series is sometimes to be observed, and the 

 mother-cells of the gemmae arise directly from the marginal cells, 

 just as in M.furcata (4, p. 277). At the time of separation the gemmae 



vary considerably in size, average 

 examples measuring perhaps 0.3- 

 0.4 mm. in length and 0.15-0.2 

 mm. in width. Most of them are 

 oblong in form, six to eight cells 

 across, and show an indistinct 

 stalk and a single apical cell. 

 Crowded rudiments of marginal 

 hairs, slightly displaced to one 

 surface, are usually present and 

 not infrequently show a paired 

 arrangement. Otherwise the gem- 

 mae are scarcely differentiated. 

 In germination (Fig. 4, B-D) 

 the young plant is at first noth- 

 ing more than a slightly narrower 

 extension of the gemma, although 

 in one somewhat older example a 

 rudimentary costa was present 

 with a wing three cells wide on 

 each side. No late stages of 

 germination have been observed. 

 The list of specimens cited 

 brings out the fact that M . divari- 

 cata, apparently on account of its 

 variability, has been confused 

 with three other species of Metz- 

 geria. In the structure of the 

 costa with its two rows of dorsal 

 and four rows of ventral cortical 

 cells it agrees with 31. conjugate and 31. furcata; in having ventral 

 hairs, sometimes produced in considerable abundance, it agrees with 

 M. corralensis. It is, however, amply distinct from all three species. 

 It differs from 31. conjugata in being dioicous and in having gemmae 



Fig. 4. Metzgeria divaricata Evans. 



A. Marginal portion of a thallus- 

 wing, ventral view, X 50. B-D. Ger- 

 minating gemmae, X 100. A was drawn 

 from the type material; B-D, from a 

 specimen collected in Chile by Neger, 

 No. 68. 





