The Genus Riccardia in Chile. 127 



above, the prostrate portion giving off a few subterete stolons and 

 an occasional new axis, the ascending portion closely pinnate to 

 tripinnate, a complex photosynthetic branch-system being thus 

 formed : ultimate branches strongly flattened, with unistratose 

 wings three or four cells wide and a thickened median portion, 

 the wings sometimes crenulate or denticulate from projecting cells, 

 composed of cells with small but distinct trigones: inflorescence 

 dioicous : S inflorescences sometimes borne singly but usually in 

 divaricate clusters of two to eight, the wings vaguely toothed, one 

 or two cells wide, the antheridia mostly six to ten : ? inflorescence 

 usually borne at the base of a more or less elongated and often sub- 

 divided branch; involucre composed of crowded teeth or cilia; 

 calyptra rough, tipped with a distinct corona : sporophyte unknown. 



Specimens examined: on rotten wood. Port Corral, 1905-06, 

 Thaxter 1^3 (H., Y.). Known only from the type locality. The 

 writer takes pleasure in naming this distinct species in honor of its 

 discoverer. Professor Roland Thaxter of Harvard University. 



Although less robust than the species already considered R. 

 Thaxteri is a relatively large plant and exhibits considerable dif- 

 ferentiation. The plants are very dark in the old prostrate por- 

 tions but are yellowish or brownish green when young and tend to 

 remain so in the photosynthetic branches. Owing to the method 

 of branching, about to be described, the thalli remain united in 

 loose but intricate tufts, closely attached at their bases to the 

 substratum. In each thallus (Fig. 2, A) a prostrate or decumbent 

 basal portion and an ascending or suberect apical portion can be 

 distinguished, although there is no sharp line between them. The 

 basal portion is essentially a rhizome and consists of a sparingly 

 branched axis, which is terete or nearly so. The branches to 

 which it gives rise are of two kinds : those which represent the axes 

 of new thalli, and those which may be regarded as stolons. The 

 latter are usually simple and soon limited in their growth ; they 

 cling closely to the substratum emitting numerous rhizoids. All 

 the branches given off from the prostrate axis arise from latent 

 rudiments in the form of blunt and often scarcely evident projec- 

 tions, covered over with slime papillae, and some of these rudi- 

 ments fail to develop into branches. The figure will give some 

 idea of the way in which the prostrate axis branches. 



The apical portion of a thallus (Fig. 2, A, B) is essentially a flat 

 photosynthetic branch-system. The subterete basal portion grad- 



