564 ALEXANDER W. EVANS 



they both show a contrast in width when the exterior and interior cells are 

 compared, the cell walls in both are thin and delicate, and the cell-measurements 

 are not very different. There are, however, certain important differences between 

 them, aside from those in texture and color. In R. brcviramosa, for example, 

 the thalli often have a regularly pinnate appearance; the secondary branches 

 rarely remain in a rudimentary condition but are usually simple; the margins 

 of the branches are commonly distinctly crenulate; rhizoids are absent or spar- 

 ingly developed; the inflorescence is dioecious, the female branch develops num- 

 erous archegonia; and the lobes of the involucre are mostly five to seven 

 cells long. In R. adglidinata, on the other hand, the branching is more irreg- 

 ular; the secondary branches often start tertiary branches, but both frequently 

 persist as rudiments; the margins are rarely crenulate, except in restricted regions; 

 rhizoids are abundantly produced; the inflorescence is autoicous; the female 

 branch bears few archegonia and sometimes but a single one; and the lobes or 

 cilia of the involucre are only one to three cells long. 



The structure of the capsule in R. adglutinata is the same as that of R. 

 vmltijida,, so far as the local thickenings of the cell walls are concerned, and 

 the species agree further in their inflorescence. Otherwise they have little in 

 common. As already noted under R. breviramosa, R. imiltifida is a narrower 

 and thinner plant, far more regularly pinnate, and the wings of the branches 

 are usually distinctly crenulate. 



Area of distribution: Endemic. 



*I0. R. insularis Schiffn. Deutsche Siidpolar-Expedition 8: 66 pi. 6 f. 

 1—7 (1906). — Fig. 2, D — H. 

 Wet rocks at low altitudes. 



Masatierra: B. Cumberland, caves V and VI, side and back walls (no. 



37. 38, 39)- 



It is with some hesitation that these specimens from wet rocks are referred 

 to R. insularis, partly because Schiffner's species was based on material from 

 the far-distant islands of St. Paul and New Amsterdam, partly because the 

 original specimens grew on the roots of ferns, and partly because bisexual 

 branches were occasionally present on these specimens but have not been de- 

 tected on the Masatierra plants. At the same time, except for this single 

 structural difference, these plants agree so fully with Schiffner's detailed de- 

 scription and careful figures of R. insularis that a specific separation seems 

 uncalled for. It may be remarked also that bisexual branches, even in species 

 where they are sometimes found, are not necessarily present on every individual, 

 so that too much stress should not be laid on their absence. 



The plants (Fig. 2, D) are a pale or dull green, turning yellowish or 

 brownish with age, and are fully as translucent in appearance as R. breviramosa. 

 They form depressed mats, becoming loosely layered in time, and produce 

 rhizoids very sparingly. The main axis, of which the living portion is 1 — 2 cm. 

 long, fs strongly flattened, being only 0.15-0.2 mm. thick although i — 2 mm. 

 wide (Fig. 2, G). From the median portion, where the cells are in only four 

 or five layers, it thins out very gradually toward the edges, which are bordered 



