288 EVANS. 



When a gemma germinates its apical cell continues (or resumes) its 

 activities and gives rise to a flat, strap-shaped thallus which tends to 

 be narrower than the gemma itself (Fig. 3, E) being often only four 

 cells wide. While this is going on the hairs on the gemma increase 

 somewhat in length, and similar superficial and marginal hairs appear 

 on the flat extension. The superficial hairs are always more numerous 

 on one surface than on the other and may be confined to one surface. 

 Sometimes the more hairy surface of the extension is continuous with 

 the hairy convex surface of the gemma and sometimes with the smooth 

 concave surface, these observations apparently showing that the 

 dorsiventrality of the gemma is not firmly fixed but that a reversal of 

 the dorsiventrality may take place at germination. 



The presence of superficial hairs on the gemmae of M. corralcnsis 

 and on the young thalli to which they give rise are perhaps the most 

 distinctive features of these structures. Except for these peculiarities 

 the gemmae and young plants are much like those of M. crassipilis and 

 M. IAebmanniana. The latter species, in fact, is closely related to 

 M. corralcnsis, differing from it mainly in its greater size; and it is 

 therefore not surprising that specimens of the Chilean species have 

 been referred to M. Licbmanniana. 



4. Metzgeria divaricata sp. now 



Grayish or yellowish green, scattered or growing in depressed mats, 

 more or less firmly attached to the substratum: thallus prostrate, 

 repeatedly dichotomous but rarely branching ventrally, plane or 

 slightly convex, well-developed thalli mostly 0.6-1.2 mm. wide, the 

 forks mostly 2-8 mm. apart; costa bounded dorsally by two rows of 

 cortical cells and ventrally by four; wings mostly eight to fifteen cells 

 broad, the cells mostly 38 X 31 /*, the walls thin or slightly thickened 

 and sometimes with more or less distinct trigones and nodular inter- 

 mediate thickenings; hairs varying greatly in abundance; marginal 

 hairs in the hairiest and most characteristic plants occurring in 

 divaricate pairs, ventral hairs under these circumstances numerous 

 on the wings and especially on the costa; hairs averaging about 0.15 

 mm. in length and 10-12 jx in width, often branched at the apex and 

 acting as rhizoids: inflorescence dioicous: d" branches sometimes 

 borne in considerable abundance, subspherical, usually bearing on 

 the ventral surface from one to five scattered hairs, 0.33-0.36 mm. long 

 and 0.33-0.45 mm. in width: 9 branch broadly obcordate, 0.25-04. 

 mm. long and 0.45-06. mm. wide, hairs abundant along the margin 



