300 



Alexander W. Evans, 



the forks, plane or slightly convex along the margins ; costa bounded both 

 above and below by two rows of cells ; wings mostly fifteen to twenty cells 

 wide, the cells thin-walled but with very minute trigones and occasional 

 intermediate thickenings, averaging about 40 X 30// and about 30^ along 



the margins ; hairs restricted to the 

 margin and to the ventral surface of both 

 wings and costa ; marginal hairs some- 

 times abundant, sometimes very scanty, 

 straight or nearly so, mostly 100 — 120 u 

 in length ; alar surface hairs and costal 

 hairs similar but a little longer, the 

 surface hairs never abundant and often 

 absent altogether : inflorescence dioi- 

 cous : 5 branch (known only from the 

 type specimen) obcordate, orbicular- 

 obovate, about 0.15 mm. long, bearing 

 a few straight marginal and surface 

 hairs : ^ branches (known only from the 

 Mexican specimens) sparingly produced, 

 globose, about 0.3 mm. long, usually 

 smooth throughout : gemmae numerous, 

 marginal, usually borne on more or less 

 ascending and tapering branches, limited 

 in growth and destitute of hairs (except 

 slime-papillae), orbicular or oblong- 

 orbicular, about 0.15 mm. wide, concave, 

 about six cells across, bearing a few 

 rudimentary marginal cilia slightlj^ 

 displaced to the concave surface, one 

 cell thick throughout and with a poorly 

 defined stalk. (Fig. i.) 



As pointed out by the writer a 

 few years ago the gemmae in the 

 genus Metzgeria^ often j'ield char- 

 acters of specific value, and some- 

 times make it possible to distinguish 

 between closely related species. In 

 M. scyphigera the gemmae are among the simplest that have been 

 described. In their development they agree in all essential respects 

 with the marginal gemmae of M. furcata (L.) Dumort., M. myriopoda 

 Lindb., and M. oligoiricha Evans, a marginal cell becoming directly 

 the mother cell of a gemma without undergoing a preliminary division. 



Figure i. — Metzgeria scyphigera 



Evans 

 A. Tip of a gemmiparous thallus, 

 X 40. B. Gemma at time of 

 separation, X 60, The figures 

 were drawn from the type 

 specimen. 



^ Vegetative Reproduction 

 i.1-16. 1910. 



Metzgeria. Ann. Bot. 24 



■i 7 1— 303- 



