OF WESTERN PENNSYLVANIA. 51 



On clay soil in fields from New England to Missouri, south 

 to the Gulf States. Occurs in eastern Pennsylvania and in 

 Ohio and so is to be looked for in our range. 



2. TREMATODON Richard. 



Autoicous, rarely dioicous ; low, singly disposed : stem with 

 a large central strand and loose ground-tissue ; leaves yellow- 

 ish-green, narrow, abruptly to gradually lance-subulate, more 

 or less crisped when dry ; costa ending below the apex or 

 percurrent; cells thin-walled, loosely elongate-hexagonal to 

 rectangular or, above, rhombic-pentagonal or -hexagonal : seta 

 yellow, erect, rarely tortuous to cygneous ; capsule with a more 

 or less long tapering neck, moderately arcuate, the urn smooth ; 

 annulus differentiated : peristome-teeth united below into a low 

 basal tube, undivided and cribrose or two-parted to the base 

 into filiform divisions, peristome rarely lacking; operculum as 

 long as the urn, obliquely rostrate ; calyptra inflated, cucullate, 

 not ciliate. 



A cosmopolitan genus of about 70 species, of which about 

 20 occur in North America, 2 of these in our region. 



Key to the Species. 



a. Collum as long as urn of capsule. i. T. ambigmis. 



a. Collum twice as long as urn. 2. T. longicoUis. 



1. Trematodon ambiguus [Hedwig] Hornschuch. 



Densely cespitose, light green to brownish-green : stems 

 short, up to 1-2 cm. high, sparsely branched, erect to ascend- 

 ing ; leaves abruptly linear-subulate from a concave ovate base, 

 flexuous, erect-spreading, the acumination canaliculate, serru- 

 late at extreme apex ; costa narrow, percurrent ; basal leaf- 

 cells laxly long-hexagonal-rectangular, hyaline, quickly nar- 

 rowed above, in the subtilation becoming small, irregularly 

 quadrate, chlorophyllose and, especially towards the apex, 

 quite obscure, in the apex the lamina forming a very narrow 

 and obscure margin along the costa; perichsetial bracts larger 

 and somewhat gradually acuminate : seta bright yellow, lus- 

 trous, 1-3 cm. long, flexuous ; including the neck the capsule 

 is clavate, arcuate-cernuous, bright orange-red ; the neck and 

 urn are each about 2 mm. long, the neck linear-cylindric, 

 somewhat strumose at base on inner side, the urn narrowly 

 oblong- to pyriform-cylindric ; peristome-teeth 16, cleft or ir- 

 regularly perforate, confluent at base; operculum about 1.5 

 mm. long, obliquely subulate-rostrate; annulus large, re- 

 voluble ; autoicous, the antheridial cluster terminal on a basal 

 branch : spores large, minutely roughened, mature in summer. 



In old fields and meadows, often in wet sandy places, in 

 Europe and, in North America, from Canada to the northern 

 United States. 



