218 HoweE AND UNDERWOOD: THE GENUS RIELLA 
In describing Riella Paulsen, the first species of the genus 
known to occur outside of the Mediterranean region, Porsild ex- 
presses the surmise that the distribution of the genus may prove 
to be still more widely extended, which is well verified by the 
known existence at the present time of three specimens of Rize//a 
collected within the boundaries of the United States. One of these, 
strangely enough, was collected by Schott as long ago as 1855, 
but has remained unstudied and unnoted in literature. In April, 
1902, western Texas, the region from which Schott’s specimens 
came, was visited by Professors F. S. Earle and S. M. Tracy, who 
secured further specimens which we consider the type of the well- 
marked species described below : 
Riella Americana sp. nov. 
Erect or ascending, 10-30 mm. high, simple or more com- 
monly 1-4 times furcate: axis elliptical in section, 0.2-0.8 mm. 
wide, mostly 6~10 cells thick, root-hairs borne only on the basal 
parts and usually few: wing 2-5 mm. broad, rounded-falciform at 
apex, slightly undulate-crisped, subentire or erose, tapering toward 
the base and commonly deficient below the first dichotomy ; cells 
near the axis about 60 in greatest diameter, those near the 
margin about 4oy: scales few, small, 0.2~-0.6 mm. long, lingui- 
form and obtuse or irregularly lanceolate and subacute, those near 
the growing apex usually intermingled with multicellular gemmae : 
gemmae trichomic in origin, soon oblong or orbicular-oblong in 
outline, showing later a median constriction and becoming finally 
panduriform and subspatulate: dioicous: antheridia about 0.3 
x 0.16 mm., sometimes as many as 75 (including empty loculi) 
in a single elongated marginal series: 9 gametophyte, or each of 
its branches, maturing for the most part 3-12 sporogonia in acro- 
petal order : involucres smooth, ellipsoidal-ovoid or at full maturity 
subglobose-ovoid, 1.4-1.8 mm. x 0.8—1.2 mm., narrowed rather 
gradually to the truncate or slightly pointed subpapillose orifice : 
capsule globose, 0.8—1 mm. in diameter, seta about 0.2 mm. long, 
mostly a trifle shorter than the ovoid-conic foot: spores dark- 
brown, 100-1304 in maximum diameter (spines included) ; outer 
face bearing numerous sometimes curved spines 10-24 long, 
with dilated apices, these spines more or less connected by radiat- 
ing basal membranes forming irregular reticulations ; inner faces 
bearing conical, non-capitate spines, 3-6 » long, with basal mem- 
branes obsolescent or entirely wanting. (/7. 17; pl. 12, f. 21, 22). 
Limpia Cafion, Texas, F. S. Earle and S. M. Tracy, April 25, 
1902, no. 251; this, the type specimen, is deposited in the her- 
