932 X. SPHAGNA. 



layer, which rests on the central or columellar tissue, divides into three concentric 

 parts in the middle, on one of which the spores are dereloped. 



The organ which forms the cap or calyptra in true Mosses, and which is merely 

 the top of the archegonium, does not take a definite shape in Sphagna. The 

 archegonial walls persist until the fruit is nearly ripe, when the primordial envelope 

 of the latter ruptures irregularly, a portion remains attached to the base, and the 

 rest, which slightly adheres to the top of the capsule, usually falls away with the 

 operculum. 



The capsule then rests immediately on the vaginula, which is usually discoid ; 

 it is separated from the perichajtium by a prolongation of the branch, so that the 

 capsule rises above the involucre ; this false pedicel, which is not (as in Mosses) an 

 integral part of the capsule, is named pseudopoclmm. 



The capsule is spherical or ovoid,* often becoming oblong by the desiccation of 

 its outer tissue. Dehiscence takes place by an operculum, which consists of a 

 horizontal section of the upper part of the capsule. When the capsule, in drying, 

 elongates and contracts, the operculum is detached with a slight crackling, and the 

 spores are expelled by the compressed air which had penetrated through the stomata 

 into the capsule. The mouth of the capsule is smooth, with no trace of a ring or 

 peristomium. 



When the fruit is perfectly ripe, the columella contracts to the bottom of the 

 capsule, and leaves the sporangium attached to the inner walls of the latter. The 

 sporiferous layer of the sporangium produces four successive^enerations [of mother- 

 cells ?] before the spores appear ; these then belong to the fifth generation. They are 

 of two shapes and dimensions : some are tetrahedral, with a convex base, and repro- 

 duce the plant ; the others, infinitely smaller, form regular polyhedrons -j^tVo ^^" ^^ 

 diameter ; these are always sterile. 



The prothallus, developed in water or on damp earth, is at first filamentous and 

 branched ; then there appear, at the extremities of one or more of its ramifications, 

 swellings, consisting of vesicular cells containing a mucilage, in which green 

 granules float; these are rudimentary plants. Under other circumstances these 

 tubercles become transformed into thalliform lobed expansions, in the sinus of which 

 young plants are also developed {Sphagnum acutifolium); in both cases recalling the 

 mode of germination of Hepaticoe, properly so-called, and of Jimgermanmew. 



ONLY GENUS. 

 Sphagnum. 



Sphagna, which formerly constituted a trihe of Mosses, and of -which the celebrated muscologist, 

 Schiujper, now makes a separate family, are, in fact, intermediate between Hepaticce and Mosses. They 

 approach the former in their mode of g'errainatlon, and in the early stages of their growth in the form of 

 the male inflorescence, the structure of the antheridia and the antherozoids, and in the absence of a 

 normal calyptra ; while they are connected with Bryacece or true Mosses by the structure of the stem 

 and leaves, the mode of ramification, the discoid vaginula, the imperfect calyptra, and the dimorphous 

 spores. 



Sphagna prefer temperate and cold countries ; they occupy an immense extent of marsh land in the 

 northern hemisphere, where their remains, accumulated for centuries, form turf, a valuable fuel in 

 countries where wood is wanting. It is in the marshy tracts inhabited by Spliagnwn that the elements 



