The Genus Riccardia in Chile. 189 



in the branch-rudiments should Hkewise be emphasized. In 

 R. tenax each rudiment shows a single lobe with the apical cell in 

 its axil; in R. jioribuuda the rudiment is a bilobed projection with 

 the apical cell in the indentation between the lobes. In its histo- 

 logical structure R. tcnax approches more closely such species as 

 R. alcicornis and R. fuscohninnca, but these are both characterized 

 by a fairly regular pinnate branching, in which branch-rudiments 

 are absent altogether or very rare in the older parts of the thallus. 

 Another species with which R. tcnax should be compared is 

 R. nudiuiitra. The histological features of both plants have nuich 

 in common, the branching is irregular in both, and the latent 

 Ijranch-rudiments in both are in the form of short lobes with the 

 apical cell in the axil. The habit of R. nudimitra, however, is 

 entirely different f'-om that of R. tcnax. It develops a prostrate 

 caudex from which the photosynthetic branch-systems are given 

 off, and in this way low depressed mats are formed. R. nudimitra 

 is further distinguished by its shorter branch-rudiments, the apices 

 of which are not concealed by the axis, and by its smooth 

 "calyptra." 



23. Riccardia pallidevirens (Steph.) comb. nov. 

 Ancura pallidevirens Steph. Bull. Herb. Boissier 7: 762. 1899. 



Specimens examined: Puerto Angosto, Desolation Island, 

 1896, Duscn i/i, i8p (N. Y., U., cited by Stephani as Aneura 

 pallidevirens, 29, p. 9). 



The species has been reported by Stephani, under the name 

 Ancura pallidevirens, from the following additional localities: 

 Huafo Island, Almirantazgo and Lake Fagnano, Tierra del Fuego, 

 Skottsberg (32, p. 7). 



In his monograph of the genus Stephani places A. pallidevirens 

 immediately before A. pinguis (L. ) Dumort., thus emphasizing 

 the slight morphological differentiation of the thallus. The plants 

 are pale green and grow in depressed mats among other bryo- 

 phytes, the thalli being loosely attached to the substratum by means 

 of scattered rhizoids or else wholly free. In spite of their fairly 

 large size the plants are delicate in texture. 



The main axis (Fig. 13, A) is prostrate or perhaps ascending in 

 the apical portion and grows indefinitely. The living portion is 



