1962] 



LEAFY HEPATICAE OF LATIN AMERIC A — PART I 



107 



walls thin or thickened and containing pits; trigones very small to large, often 

 coalesced ; a vitta of larger cells present in some species ; cuticle smooth to ver- 

 ruculose. Underleaves quadrate, elongate to ovate, sometimes cordate at the base, 

 the line of attachment transverse or recurved, in some connate with leaves on 

 one or both sides, the apex rounded-entire to 2-4-toothed or -lobed, or variously 

 incised, the margins entire, crenulate, spinose-dentate to ciliate. Plants dioicous, 

 the sexual branches short, ventral, intercalary, axillary; male branches catkin- 

 like, the bracts ovate, concave, bilobed to bispinose, the bracteoles slightly smaller, 

 plane ; antheridia one or two ; female branches solitary, the bracts and bracteoles 

 in three or four series, unlike the leaves, orbicular-ovate to ovate-lanceolate. 

 Perianth to 6 cm long, ovoid-cylindric, terete below, trigonous and of a single 

 layer of cells above, often with additional folds, the mouth of three ciliate to 

 dentate lobes, usually contracted. Sporophyte capsule oblong-ovoid, the wall 

 usually of five layers, the outermost layer with brown thickenings as knots along 

 the vertical walls, the innermost layer with brown thickenings as half-rings or 

 bands on the inner tangential walls; capsule-stalk with an outer layer of 16 

 large cells surrounding many smaller cells ; spores small, brown ; elaters long, 

 slender, bispiral. Sporeling of the Nardia type. Vegetative reproduction by 

 means of leafy shoots from cylindric protonemata from cells of ordinary or 

 caducous leaves and underleaves. 



Type species: Jungermannia trilobata. 



This large genus is most abundant in tropical and subtropical regions, with 

 a few species extending northward into the Northern Hemisphere, or southward 

 from the tropics. It is easily recognized in the field because of the apparent 

 dichotomies of the stem, the ventral flagelliform branches, the incubous leaf 

 arrangement, the usually three-toothed leaves, and the conspicuous underleaves. 

 Unfortunately, it is much more difficult to recognize many of the species, for 

 most of them are exceedingly variable, as Spruce (1885) has pointed out. This 

 variation is more than habitat modification, and is often so extreme among the 

 plants of different areas, or even between male and female plants, that the 

 limits of certain taxa have been established on a more or less arbitrary basis. 



The genus appears to be an old one, since there are two easily recognized 

 subgenera and six sections, and the distribution patterns of groups of species, 

 or of individual species, are often localized or discontinuous. A number of 

 species have an Antarctic distribution. 



Key to the Species 



A. Leaves predominantly 2-toothed. (subg. BideMatae) 



Stems coarse-thread-like to delicate-filiform, slender; in green to dark green mats. 



Leaves caducous, vitiate; underleaves small, distant, scarcely divided. 7. B. gracilis. 



Leaves persistent, often reduced or deflexed. 



Leaves with a vitta of larger thin-walled cells with conspicuous trigones. 



Underleaves scarcely as broad as the stem, the apex faintly lobed or toothed. 



7. B. gracilis. 



Underleaves mostly broader than the stem, irregularly and coarsely incised or 

 toothed; teeth of the leaves with crenulate margins; vitta not very 

 conspicuous. 2. B. phyllobola. 



Leaves without a well-marked vitta. 



Cells of the apical portion of the leaf mostly (18)24-36 /i, the trigones very 



large and rounded. 6. B. roraimensis. 



Cells of the apical portion of the leaf mostly 18-24 n, the trigones small, 



conspicuous. 4. B. cuneistipnla^ 



