SPHAGNACEAE. 431 



Order 1. SPHAGNALES. 



Protonema normally thalloicl, the gametophyte developing from its 

 edge; the latter at first branchless, but branches soon developing, usually 

 in fascicles of 3 or more. Archegonia borne on more or less differentiated 

 branches; antheridia on normal or slightly differentiated ones. Calyptra 

 rent irregularly by the ripening capsule, leaving at its base an inconspic- 

 uous sheath. Capsule nearly sessile, globose, on a very short stalk with a 

 bulbous base; capsule at maturity raised upon a prolongation of the fruit- 

 ing branch (pseudopodium), dehiscent by a small apical lid; peristome 

 none; endothecium giving rise only to the columella, upon whose broad 

 rounded top rests the dome-shaped spore-sac. Spores tetrahedral. The 

 order consists of but one family. 



Family 1. SPHAGNACEAE Nees. 

 Peat-moss Family. 

 Characters the same as those of the order. Only the following genus. 



1. SPHAGNUM [Dill.] L. 



Large erect mosses mostly of bogs, and wet mountain summits. Plants 

 developing apically. Branches usually in fascicles disposed spirally about the 

 stem, densely crowded together near the apex. Leaves of the stem and 

 branches arranged spirally, composed of a single layer of two kinds of cells. 

 Stem-leaves more or less differentiated in shape and size, less closely disposed 

 than the branch-leaves. Plants monoicous or dioicous, the antheridial and 

 archegonial branches always distinct. Antheridia long-pedicellate, globose to 

 oval, borne each at the side of a perigonial leaf, opening at the summit when 

 mature and releasing vesicles containing each a spermatozoid ; paraphyses lack- 

 ing. Archegonial branches single or rarely two together, bearing at the apex 

 without paraphyses 1-5 archegonia, of which after fertilization only one de- 

 velops into a capsule. Perichaetial leaves much larger than and usually other- 

 wise differentiated from the other leaves, enclosing the capsule until its 

 maturity; capsule globose, dark-brown to black, with small lid, without annulus 

 or peristome; spores tetrahedral, disseminated by explosive discharge from 

 the capsule. [Greek, in reference to the spongy nature of the plants.] About 

 250 species, of wide geographic distribution. Type species: Sphagnum 

 palustre L. 



Stem-leaves large, long-lingulate ; branch-leaves oval to ovate. 1. S. magcUanieum. 

 Stem-leaves small, triangular-ovate ; branch-leaves long- 

 lanceolate or linear-lanceolate. 2. S. cusijidatutn. 



