90 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN [VOL. 11 



or mats; stems slender, to 4 cm long, with leaves to 3 mm wide, irregularly 

 branched, the branches ventral-intercalary, long, leafy or flagelliform ; stem in 

 transverse section with the cells of the cortical band in one or two layers, thick- 

 walled and smaller than the cells of the medulla. Rhizoids not seen. Leaves 

 widely spreading, long, narrowly ovate to oblong-ovate, to 1.3 mm long, to 6 mm 

 wide, asymmetric, the dorsal margin convex, entire, or with an occasional tooth 

 near the base, the ventral margin with spines and cilia in the lower half, the 

 ventral base more or less auriculate, bifid to one-fifth or one-fourth of their 

 length; segments triangular from a 4- to 6-celled base, acute, the sinus broad, 

 rounded ; leaf -cells of the base of the segments 18-28 X 18 /*, the walls uniformly 

 thickened, the trigones small, the cuticle coarsely papillose. Underleaves ovate, 

 to 5.06 mm long, 0.3 wide (the lamina), less than half the length of the leaf, 

 bifid, the margins long-spinose to ciliate. Plants dioicous. Male inflorescence 

 terminal (becoming intercalary?), the bracts and bracteoles in few pairs, simi- 

 lar to the leaves and underleaves, slightly larger, more or less pouched, antheridia 

 in the axils of both the bracts and bracteoles. Female inflorescence and sporo- 

 phytes not seen. Fig. 4, a-f . 



Habitat: On bark and branches in humid forest. 



JUAN FERNANDEZ: Masatierra, above Plazoleta del Yunque, C. $ J. Skottsberg 

 (type S-PA). 



Taxa not seen: 



Isotachis georgiemis var. fuegiensis. Gola, Nuovo Gior. Bot. Ital. 29: 170. 1923. 



Herberta 8. F. Gray. Nat, Arr. Brit. PI. 1: 705. 1821. 



Schisma Dumortier, Comm. Bot. 114. 1822. 



Sendtnera C. G. Nees in G. L. & N. Syn. Hep. 238. 1844. 



Leafy plants yellowish to brown, often becoming reddish or purple, ascend- 

 ent to erect, or pendent, from a prostrate rhizome (often obscure) with scale- 

 like leaves ; leafy stems of medium size or robust, to 30 cm long, or thin and deli- 

 cate and very short, sparingly irregularly branched ; branches rarely lateral, of 

 the Frullania type, with the lanceolate half-leaf at the dorsal base, more fre- 

 quently intercalary, from the axils of the underleaves or from the stem at the 

 ventral base of the leaf or either side of the underleaf, leafy or flagelliform; 

 stem in transverse section with a cortical band of one to three layers of cells 

 with thick, deep brown to yellow walls, and a medulla of many larger cells with 

 progressively thinner Avails toward the middle, the pits numerous. Rhizoids 

 thin-walled, from cells of the lower part of the underleaf or the scale-leaves of 

 the flagelliform branches. Line of leaf insertion transverse. Leaves elongate 

 to subquadrate, symmetric to asymmetric, deeply bifid (rarely trifid), the seg- 

 ments linear to lanceolate, the margins entire, serrate, toothed or appendiculate, 

 especially near the base; vitta of narrow, elongate, thick- walled cells always 

 present, bifurcating near the base of the leaf or just below the sinus, ending 

 below the tips of the segments or in the tips; oil bodies four to eight per cell 

 (at least in some species) round to oval, homogenous. Underleaves as large as 

 the leaves, similar, symmetric. Plants dioicous. Male inflorescence terminal be- 

 coming intercalary on the stem, the bracts and bracteoles like the underleaves, 

 pouched ; antheridia large, spherical, usually in pairs in the axils of both the 

 bracts and the bracteoles, the stalk of two rows of cells. Female inflorescence 

 terminal on the leafy stem or long branch, with one or two subfloral innova- 

 tions of unlimited growth, the inflorescence appearing to be on a short lateral 



