20 American Midland Naturalist Monograph No. 6 



Order I. Sphagnales — Peat Mosses 



Characteristic peat mosses, in bogs, usually either in water or water-soaked, 

 monoicous or dioicous, deeply cespitose, the tufts constantly growing upwards 

 at the same time that the plants are dying from below and often thus giving 

 rise to deep beds of peat, the tufts light grayish-green or sometimes yellowish, 

 often more or less tinted with red above: stems without rhizoids, usually com- 

 posed of an outer cuticular sheath consisting of one to three or four layers of 

 large lax cells, an intermediate hollow cylinder composed of prosenchymatous 

 cells with usually thickened walls, and a central pith of lax parenchymatous 

 cells; branches symmetrically fascicled, usually partly divergently spreading 

 and partly slender and appressed-pendent; leaves ecostate, unistratose, com- 

 posed of large, hyaline, more or less elliptic cells with usually perforated and 

 spirally thickened (fibrillose) walls and separated by narrow chlorophyllose 

 cells which meet at their ends to form a continuous network throughout the 

 leaf; stem-leaves usually different in form from the branch-leaves, remote, 

 often lacking entirely the pores and spiral fibrils, while the branch-leaves are 

 usually porose, fibrillose, and more or less densely imbricated; seta none but 

 the capsule is borne upon an outgrowth from the gametophyte termed a pseu- 

 dopodium; antheridial flowers usually at the ap£x of specialized branches of 

 the capitulum, the antheridia being pedicillate, globose, and solitary at the 

 base of the bracts; the archegonial flowers gemmiform, axillary in one of the 

 upper fascicles, only one of the three or four archegonia developing, as a rule: 

 capsule globose, castaneous, with a convex operculum, without annulus or 

 peristome; calyptra irregularly lacerate; spores developed from the amphithe- 

 cium, the columella from the endothecium. 



This order is a peculiar one comprising but one family {S phagnaceae) 

 which contains but the one genus {S phagnum) with about 340 known species. 

 The Sphagnums are cosmopolitan in suitable habitats but are most abundant 

 in the cooler temperate regions of Europe and North America, in both of 

 these countries often forming bogs of large areas. In North America there 

 are known about 40 species, at least 30 species or varieties in our range. 



The following treatment follows closely that of C. Wamstorf in Die Na- 

 tiirlichen Pjlanzenjamilien 1(3): 248-262. 1900. Also frequently consulted 

 was Sherrin, W. R. An Illustrated Handbook of the British Sphagna. 1927 

 and Andrews, A. LeRoy. Sphagnales. North American Flora 15:1-31. 1913. 



I. Sphagnum [Dillenius] Hedwig 



(Revised with the assistance of Charles M. Boardman) 



Analytical Key to the Species 



A. Branches in tufts of 6-12 with 3-5 of them spreading; branch-leaves narrowly ovate- 

 lanceolate, narrowed to an involute-tubulose point 6. S. Wulfianum 



A. Branches in tufts of 2-6, with 2 or sometimes 3 of them spreading B 



B. Cuticular cells of stems and branches spirally fibrose; branch-leaves cucullate at 



the apex, which is obtuse and entire, rarely acute C. (Cymbifolia) 



