520 
fering in being smaller and more delicate (dorsal lobes of leaves 
.85-1.2 mm. X .5—.85 mm.), and in the subrepand-dentate margins 
of dorsal and ventral lobes and underleaves. 
Exsicc. Musc. Allegh. 265. 
Adhering to decayed logs, bank of the Watauga River, near 
the base of Grandfather Mt., North Carolina (Sullivant). Col- 
lected but once. The ventral lobe often appears to be inserted a 
little lower upon the stem than the dorsal. The fascicles of root- 
lets mentioned by Sullivant as a distinguishing character are some-. 
times better developed in the true Porella pinnata than in this. 
4. PoRELLA RIVULARIS (Nees) Trevis. Mem. r. Ist. Lomb. IT. 4: 
407. 1877. 
Madotheca rivularis Nees, Naturgesch. Eur. Leberm. 3: 196. 
1838. 
Porella dentata Lindb. Act. Soc. Scien. Fenn. 9: 342. 1869. 
Dull, or very rarely a little polished, opaque, commonly dark 
green, sometimes yellowish, mostly soft and flaccid: stems irregularly 
pinnate or subdichotomous, 3-10 cm. long, prostrate or ascending, 
forming loose or more dense mats, branches somewhat obtuse, 
scarcely diminishing in width toward apex : dorsal lobes of leaves 
usually subimbricate or approximate, sometimes distant, rarely 
closely incubous, obliquely ovate to orbicular-ovate, rounded-ob- 
tuse, I-2 mm. x .8-2 mm., entire or subdenticulate, flat or slightly 
concave beneath, only a little decurved at the apex, trigones mostly 
small; ventral lobes small, obliquely ovate, acute, .35-.7 mm. 
X.12~.4 mm., length ze the width of the dorsal, about one-half 
as broad as the underleaves, margins, especially the outer, for the 
most part broadly revolute, often giving the lobe a twisted appear- 
ance, long decurrent, usually dentate or subciliate at base inter- 
nally and sometimes unindentate externally but scarcely spurred ; 
underleaves distant, quadrate, orbicular to broadly ovate, about 
twice the width of the stem, apex rounded-obtuse, sometimes re- 
flexed, margins repand-undulate, very long decurrent, the wing 
sometimes exceeding the free portion in length and usually acutely 
dentate or subciliate: dioicous: ¢ spikes oval to oblong, 1.5-2-5 
mm. in length; ¢ branch short ; ventral lobes of the single pair of 
bracts acute or subobtuse, entire or repand, the dorsal obtuse, 
bracteole ovate-linguiform, repand; perianth ovate, with lateral 
margins deflexed, deeply bilabiate, the lips subentire or repand- 
dentate, usually plane : spores 27-45 p, papillate-echinulate ; ela- 
ters 180-290 x 8-10 y, rather obtuse, 2-(3-) spiral. ; 
