CHILEAN SPECIES OF METZGERIA. 295 



thallus is mostly 0.5-0.9 mm. wide and attains a length of 1-1.5 cm. 

 The wings, although described as almost revolute by Stephani, are 

 flat or even slightly concave and are mostly six to twelve cells wide. 

 The normal branching is dichotomous with the forks 2-10 mm. apart, 

 but ventral branching is not exceptional. 



The marginal hairs vary greatly in abundance. In some places they 

 may be absent altogether; in other places, even on the same thallus, 

 they may be as numerous as the marginal cells, a single hair arising 

 between every two cells. In most cases the hairs are slightly displaced 

 to the ventral surface, but they may be truly marginal, and it is not 

 unusual for the apex to be branched and to act as an organ of attach- 

 ment. The longest hair seen was 0.3 mm. long but most of them were 

 0.1 mm. or less in length, the average diameter being about 10 m- 

 The ventral surface of the wings is apparently wholly free from hairs, 

 but the costa bears them in loose clusters or scattered and is rarely 

 free from hairs for any great distance. These costal hairs are essen- 

 tially like the marginal hairs but tend to be a little longer. 



The costa is bounded both dorsally and ventrally by two rows of 

 cortical cells, a type of structure found also in all the following species. 

 The alar cells average about 35 X 27 m, although Stephani's measure- 

 ments gave 54 X 36 m- The walls are slightly thickened and some- 

 times show minute trigones and occasional nodular intermediate 

 thickenings. 



According to Stephani the inflorescence is dioicous. The type 

 specimen, however, is clearly autoicous, the male and female branches 

 often occurring in close proximity. The male branches are mostly 

 0.3-0.4 mm. long and 0.25-0.3 mm. wide and are ellipsoidal inform, 

 the margins being involute and the costa so strongly incurved that it 

 approaches the base without reaching it. Except for the slime- 

 papillae the surface is smooth. The female branches, which are more 

 or less concave and obcordate in outline, are mostly 0.4-0.45 mm. long 

 and 0.45-0.6 mm. wide. The marginal hairs grow out from small 

 cells but are not numerous; the ventral hairs may be restricted to a 

 cluster of six to twelve on the thickened median portion, but one to 

 three scattered hairs may be present also on the wings. No gemmae 

 have been observed. 



The autoicous inflorescence will at once distinguish M. chikmsis from 

 all the other Chilean species. It agrees in this unusual feature with 

 M. conjugata, but in that species the ventral cortical cells of the costa 

 are in four rows and the marginal hairs often in pairs. The only other 

 South American species to which an autoicous inflorescence has been 



