OF WESTERN PENNSYLVANIA 283 



rarely carinately split, cilia usually 1 or 2, usually considerably 

 shorter than the segments ; annulus none ; spores mature in 

 summer. Very variablfe and split up into many forms and 

 varieties by various authors. 



In ditches, swamps, bogs, stagnant pools, etc., often im- 

 mersed or floating, almost cosmopolitan in temperate and cold 

 regions ; in North America, throughout Canada and the north- 

 ern United States. Rare in our region. 



Center : fiear Meadows. T. C. Porter. (Porter's 



Catalogue). 

 McKean : West Branch Swamp, Bradford, in stag- 



nant pools among willows, June 9, 1895. 

 I\ A. B. 



4. Drepanocladus exannulatu§ (Guembel) Warnstorf. 



(Hypnum exannulatum Bryologia Europsea; Amblystegium ex- 

 anmilatus DeNotaris). 



(Plate XL) 



Typically more rigid, compact, and more completely pinnate 

 than D. fluitans, the leaves more falcate, usually serrulate, fre- 

 quently striate, especially when dry : the costa reaching well to- 

 wards the apex and rather stronger than in D. fluitans, biconvex ; 

 the alar cells hyaline and much enlarged, forming an excavate 

 and well defined patch extending across to the costa. In our 

 region the specimens show the following characteristics : yel- 

 lowish-brown, floating, the stems up to 8 or 10 cm. long, the 

 tips of stems and branches hooked ; leaves rather remote, reach- 

 ing 4 mm. long, irregularly and widely spreading, not definite- 

 ly circinate or secund, except at the tips of stems and branches, 

 slenderly acuminate into a sub-channeled acumen, entire, the 

 base rounded to somewhat excavate and decurrent auricles, so 

 that the insertion is more or less of a semi-circle ; median leaf- 

 cells linear, rather incrassate, about 10-15 :1, reaching 0.3 mm. 

 or even longer, towards the base rapidly becoming shorter 

 and quickly passing into large, hyaline, oblong, much-inflated 

 cells, thus forniing a distinct patch reaching to the costa and, 

 below, passifi^ abruptly into the narrowly linear epidermal 

 cells of the stem ; in cross-section the stem may be seen to have 

 the 3 or 4 outer layers small and vfery thick-walled. 



In bogs and wet places, usually in cool or alpine regions ; 

 northern and temperate Europe and Asia and, in North 

 America, from Greenland to Alaska south to the northern 

 United States. Only once found in our region. 



Crawford : In pools, Pymatuning Swamp, Linesville, 



August 19, 1904. Sterile. O. E. J. (Fig- 

 ured). 



