CHILEAN SPECIES OF METZGERIA. 



311 



develop new costae (Fig. 9, A), sometimes retaining them as long as 

 growth continues and sometimes losing them before growth is brought 

 to an end. It will be seen from 

 this account that the gemmipar- 

 ous branches exhibit a wide range 

 of variability. 



The first gemmae to be pro- 

 duced are marginal and arise in 

 acropetal succession, every margi- 

 nal cell in extreme cases giving 

 rise to a gemma. If the gemmi- 

 parous branch shows the more 

 specialized features described 

 above, some of the later gemmae 

 may be given off dorsally from 

 the submarginal alar cells and 

 perhaps also from the cortical cells 

 of the costa both dorsally and 

 ventrally, the acropetal succession 

 in such cases not persisting. In 

 instances of extreme production 

 the crowded gemmae extending 

 in all directions almost conceal the 

 tip of the slender gemmiparous 

 branch, although even then the 

 apical cell of the branch can us- 

 ually be clearly distinguished. 



At the time of separation the 

 gemmae vary considerably in size, 

 but an average example measures 

 about 0.12-0.1 mm. and is five 

 cells across. It is oblong in out- 

 line and strongly convex, the 



Fig. 9. 



Metzgeria violacea 

 Dumort. 



(Ach.) 



A, B. Gemmiparous branches, ven- 

 tral view, X 50. C. Gemma about 

 ready to separate, X 100. D. Germi- 

 nating gemma, X 100. A was drawn 

 from an unnumbered specimen labelled 



whole margin (including the single M. angusta and collected at Punta 



apical cell and the indistinct stalk) Arenas by Dusen; B-D, from a , speci- 



, . , ,-r, „ ^x r, men collected at the same locality by 



being revolute (Pig. 9, C). On Thaxter, No. 159. 



each side three or four short rudi- 

 ments of marginal hairs can be distinguished; these normally arise 

 between every two marginal cells and may be borne singly or (more 

 rarely) in pairs. Otherwise the gemmae show no cell-differentiation 

 and are unistratose throughout. 



