930 X. SPHAGNA. 



Moss-like soft flaccid spong Acotyledons. STEMS erect in bogs, floating in swamps ; 

 BRANCHES regularly fascicled, attached to the stem laterally to the insertion of the 

 leaves. LEAVES imbricate, concave, nerveless, uncolonred and nearly transparent. 

 REPRODUCTIVE ORGANS composed of antheridia and archegonia. ANTHERIDIA situated 

 on long-pedicelled amentiform branchlets, opening elastically at the top, and emitting 

 antherozoids. ARCHEGONIA terminal, in bud-like involucres. FRUIT solitary, capsular, 

 globose or ovoid, sessile on a hemispherical or sub-discoid vaginula. Calyptra forming 

 a very imperfect cap, the largest part remaining attached to the vaginula. CAPSULE 

 operculate ; peristome naked, without annulus. SPORANGIUM hemispheric, seated on a 

 very short thick columella, which disappears loTien ripe. SPORES dimorphous, some 

 larger, pyramidal, the others polyhedral. PROTHALLUS filamentous, Jcnotty or lobed, 

 analogous to that of Hepaticse. 



STEM. Composed of a woody cortical cylinder of fibrous cells, surrounding a 

 medullary or axile bundle. The cortical cylinder formed of 1-4 layers of sometimes 

 fibrous cells, nearly always pierced with annular holes, which by facilitating capillary 

 action in the stem and branches, enable the plant to grow without roots, and to 

 rise to a considerable height, often many feet above the soil, without loss of vegeta- 

 tive power ; this result is principally due to the reflexed branches, which always 

 remain sterile, and which, acting like adventitious roots, contribute, with the spongy 

 tissue of the bark of the stem, to raise the water from the base of the plant to 

 its top. 



ROOTS or rootlets only exist in young plants, completely disappearing after- 

 wards ; they are composed, as in true Mosses, of a single series of cylindric hyaline 

 cells. 



LEAVES. The leaves are not developed from the cortical layer of the stem, but, 

 like the branches, from the outer cellular layer of the woody cylinder. Cellular 

 tissue uniform, but subsequently dimorphic, owing to the unequal segmentation 

 of the cells, of which some become elongated, and contain chlorophyll ; others tabular, 

 diaphanous and porous. This structure is analogous to that of true Mosses, but 

 in Sphagna the two kinds of cells are distributed in the same layer, and alternate 

 with each other, so that the cylindrical green cells form the threads of the foliar 

 network, and the large porous cells form the interstices. The cells pierced with 

 holes are evidently intended, like those surrounding the stem, to render the plant 

 more hygrometric. With the exception of Leucophanes, no Moss possesses a greater 

 power than Sphagna do, of conveying water to considerable heights ; they are true 

 siphons, contributing to the draining of marshes, converting swamps into bogs, and 

 bogs into dry land. 



REPRODUCTIVE ORGANS. Antheridia and archegonia (like true Mosses and 

 Hepaticce), usually on different individuals, never in the same involucre, as is so 

 often the case with Mosses. Antheridia collected in inflorescences (the only analogue 

 to which is in the leafy Hepaticce), forming catkins or small cones, situated on 

 secondary axes. Each inflorescence is composed of an involucral leaf, and an antheri- 

 dium inserted laterally to this leaf. The antheridia greatly resemble in form those 

 of Hepaticce ; they are globose or ovoid sacs, formed of one layer of hyaline chloro- 



