CHILEAN SPECIES OF METZGERIA. 



281 



to the margin. In most cases this description applies, but occasion- 

 ally a few scattered hairs arise from the ventral surface of the costa. 

 The crowded marginal hairs, as he notes, occur singly and are usually 

 straight. In well-developed plants a hair (Fig. 2, A) is found between 

 every two marginal cells, and when the revolute wings approach each 

 other closely the hairs form a delicate weft between them, making it 

 difficult to study the features of the costa without spreading the wings 



Fig. 2. Metzgeria decrescens Steph. 



A. Part of a slender thallus, ventral view, X 50; there are only two or 

 three rows of cortical cells, the external stippled row on each side representing 

 a bistratose transition-region between costa and wings. B-E. Transverse 

 sections of costae, X 100. F. Male branch, X 100. G. Costa and adja- 

 cent alar cells of a male branch, showing slime-papillae, X 100. The figures 

 were all drawn from the type material. 



apart. The hairs are mostly 0.2-0.4 mm. long and 10-20 /j. in width, 

 tending to taper from the base. 



The alar cefls have thin or slightly thickened walls, and trigones 

 are either absent or minute and inconspicuous. Stephani gives the 

 size of the cells as 54 X 45 jx. According to the writer's measure- 

 ments the average size of the cells in the type specimen is about 45 X 

 34 (j., while the general average derived from the eight specimens listed 



