﻿of North America. 21 



Monoicous. Sporogonia chiefly marginal, but becoming now and 

 then dorsal, wholly or for the greater part enclosed within the involu- 

 cre, suberect or horizontal-deflexed. Capsule short, oblong-sphaer- 

 oidal to elongate-cylindrical, bivalved or opening irregularly, with" 

 out stomata ; columella sometimes early disintegrated and obscure ; 

 spores often nearly smooth ; sterile cells single or irregularly ad- 

 herent, hyaline, nearly cubical, usually with traces of spiral thick- 



enings 



Key to the Species 



Spores smooth or nearly so. 



I. N, orbicularis, 



Spores muriculate, at maturity fuscous or nearly black. 2. N. Breutelii. 



I. Notothylas ORBICULARIS (Schwein.) Sulliv. Muse. Allegh. 



. [Exsicc] subjoined to no. 290. 1845. 



Targionia orbicularis Schwein. Spec. Fl. Am. Sept. Crypt 23. 

 1821. 



Carpobohis orbicularis Schwein. Jour. Philad. Acad. 2: 370.//., 

 f. II. 1822. 



Notothylas valvata Sulliv. Muse. Allegh. [Exsicc] 289. 1845. 



Notothylas melanospora Sulliv. I.e. 290. 



Thallus forming flat, often confluent rosettes 5-16 mm. in di- 

 ameter, deeply lobed, undulate-crisped, often with narrow as- 

 cending marginal laciniae, ridged and pitted but scarcely lamellate, 

 4-8 (rarely 12) cells thick in axile parts, with large lacunae, be- 

 coming sometimes widely 3- or 2-stratose toward the margin ; 

 surface-cells distinct, protuberant, quadrate, rhombic, or oblong- 

 hexagonal, 40-145 X 30-40 i±\ involucres commonly at the mar- 

 ginal sinuses, becoming sometimes distinctly dorsal, often gemin- 

 ate, corniform, horizontal-deflexed, more rarely suberect: capsule 

 widening a little below the middle, ovate- or oblong-cylindrical, oc- 

 casionally oblong-ovoid, .75-3.25 X -35-.65 mm., with or without 

 distinct lateral sutures, bivalved or opening irregularly, the exterior 

 cells oblong or irregularly quadrate, usually very thick-walled, 

 those bordering the valves yellowish-brown and more solid ; colu- 

 mella often fuscous and appendiculate; spores rounded-tetra- 

 hedral, 36-50 a in maximum diameter, yellow, becoming at times 

 nearly black, smooth or very obscurely roughened on the convex 

 face; sterile cells difform, mostly single and subcubical, with rudi- 

 ments of spiral thickenings. 



Exsicc. Muse. Allegh. 289, 290; Hep. Bor-Am. 124, 125; 

 Hep. Am. 65. 



