286 



EVANS. 



may be as much as 2.5 mm. in well-developed plants. The wings are 

 plane or somewhat convex and are mostly fifteen to twenty-five cells 

 across in the type material, although Stephani gives the width as 

 only twelve cells. According to his statements the alar cells measure 

 36 X 27 /x, and these figures agree pretty closely with the general 

 average of 33 X 26 n, obtained from the five specimens listed above. 

 The cells, as he notes, are essentially thin-walled throughout, although 

 vague indications of trigones are sometimes present. 



In well-developed thalli the whole ventral surface, including both 

 the costa and the wings, is covered over with crowded hairs, giving 

 it a pubescent appearance. These hairs are mostly 0.1-0.3 mm. in 



Fig. 3. Metzgeria corralensis Steph. 



A. Part of a thallus showing costa and adjoining cells of wings, dorsal 

 view, X 50. B. Transverse section of costa, X 100. C. Costa and 

 adjoining alar cells of a male branch, showing ventral hairs, X 100. D. 

 Gemma at time of separation, X 100. E. Germinating gemma, X 100. 

 A, D and E were drawn from a specimen collected on the Osarno Volcano; 

 B and C, from a specimen collected at Arique by Lechler. 



length and 10-12 fj, in diameter. Those along the margin, which are 

 essentially like the others, sometimes spread widely and sometimes 

 grow downward; they usually arise singly, as Stephani notes, but 

 twinned hairs may occasionally be demonstrated. Between the 

 densely pubescent ventral surface, which is doubtless typical for the 

 species, and a smooth or nearly smooth condition, all gradations occur, 

 although it is doubtful if a thallus is ever smooth throughout. 



In the specimens studied by the writer a few male branches are pres- 

 ent and are mostly 0.2-0.35 mm. in length by 0.25-0.4 in width. The 



