162 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 
Sete straight; megaspores alveolate or rugose-retic- 
ulate. 
Plants erect; stems up to 1 mm. thick ; megaspores 
rugose-reticulate________________--___ 1. S. riddellii. 
Plants ascending; stems thicker; megaspores 
alveolate__________________-- 8. S. rupestris. 
1. Selaginella riddellii Van Eseltine, sp. nov. PLATE 15. FIGURE 63. 
Plants erect or ascending, cespitose, 4 to 8 cm. (occasionally 12 cm.) high; 
rhizophores few, 1 to 5 cm. long (averaging 2 cm.), finely and copiously short- 
radicose; stems (including leaves) 0.7 to 1.2 mm. thick, rigid, branched at in- 
tervals of 6 to 12 mm.; branches few (2 to 4), 2.5 to 6 cm. long, with few 
branchlets, these simple, strictly ascending, up to 5 mm. long; leaves apparently 
6-ranked, appressed, slightly imbricate, pale green when young, ochraceous to 
dark brown in age, thickish, flat or slightly concave on the upper surface, 
eR 
TAS 
Ny We 
WARN gy Pog, 
AN. 
Wht 
MA OY 
* 
uN 
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Fic. 63.—Details of Selagmella riddellii. a, Dorsal view of leaf; b, ventral view; 
e, dorsal view of sporophyll; d, ventral view; e, commissural face of megaspore ; 
f, outer face. From the type specimen, Scale 30. 
slightly convex on the lower, deeply sulcate dorsally in a median line up to the 
rather blunt apex, linear-deltoid to linear-lanceolate from a short obdeltoid 
base, minutely 4 to 8-ciliate on the margins; longest leaves 1.3 mm. long; cilia 
up to 0.06 mm, long, green, yellowish, or hyaline; sete up to 0.6 mm. long, on 
the younger leaves white, on the older leaves reddish or yellow at the base, 
scabrous to spinulose-roughened. 
Spikes nearly quadrangular, up to 2.5 em. long; sporophylls up to 1.5 mm. 
long, 0.7 to 0.8 mm. wide just above the base, slightly elongate-triangular from 
an auriculate base (auricles rounded-triangular), minutely 12 to 18-ciliate on 
the margins; sets and cilia similar to those of the stem leaves, 
Megasporangia yellowish, 0.6 mm. in diameter; megaspores 0.45 mm, in diam- 
eter, yellowish, rugose-reticulate; microspores deep orange (deep yellow by 
transmitted light), up to 0.046 mm. in diameter. 
Type in the U. S. National Herbarium, no, 690149, collected near Prairie 
View, Waller County, Texas, January 3, 1911, by F. W. Thurow (no. 7). 
