VI. LYCOPODIACE^. 911 



or distichous^, imbricate. Eeproductive organs of two inds, similar to those of 



MarsileacecB, inserted at the base of the fronds. Antheridia and sporangia enclosed 



in distinct sporocarps [conceptacUs], globose, 1-celled, composed of 2 laminae with 



intervening empty laminae. Antheridia spherical, springing from a much-branched 



basilar column. Sporangia ovoid, pedicelled, at the top of a central clavate column. 



The only'spore developed in the sporangium emits a prolhallus, on which several 



archegonia are usually developed. 



GENEEA. 



Azolla. Salvinia. 



iSah'iuiecB, which formerly composed, with Marsileacece, the family of Rhizocarpece, differ from Marsi- 

 leacece and PikilaricB in habit, and in reproductive organs, which occupy distinct one-celled sporocai'ps 

 with central placentation ; also in the sporocarp not producing mucous bodies, and in its decaying 

 when ripe. 



These plants float on still water lilse Lemna. 



Salvinia is met with throughout the northern hemisphere, as well as in tropical and South America. 

 Azolla inhabits Asia, Africa, Australia, and America from Canada to the Straits of Magellan. 



VI. LYCOPODIACE^. 

 (LTCOPODiNBiE, 8wartz, Br. — Ltcopodiaob^, L.-O. Richard, Brongn., Spring.) 



Acotyledonous terrestrial moss-like plants. Stem herbaceous, rooting or creeping, 

 simple or branched. Leaves opposite or whorled, persistent, small, l-herved. Frxtoti- 

 FICATION epiphyllous at the base of the leaves, and dispersed over the entire stem, or 

 arranged in cathins at the ends of the branches. Sporangia sessile, or shortly stipi- 

 tate, reniform or cordate, coriaceous, 2-3-valved, containing either powdery quaternary 

 granules, smooth or papillose, or larger granules, marhed on one side with 3 prominent 

 lines. 



Terrestrial perennials, or very rarely annuals, resembling Mosses or Junger- 

 mannias. EooTS filiform, at first simple, then dichotomous, exceptionally fusiform 

 {Phylloglossum). Stem herbaceous, leafy, rooting, creeping or erect or sometimes 

 sarmentose {Selaginella scandens, Lycopodium volubile), simple or dichotomously 

 branched. Axis formed of scalariform vessels, arranged in bundles, the number of 

 which is a multiple of 2 (4, 8, 16, 32, 64), and the division of which produces a 

 dichotomous ramification of the stem, as in Ferns. 



LycopodiacecB are divided by their habit into two natural groups : the one has 

 branches developed in all directions, or at least in undetermined directions (true 

 Lycopodda, Psilotum, Tmesipteris); in the other the branches spread symmetrically, 

 forming a sort of frond analogous to that of some Ferns (Selaginella). Some 

 species have a compressed stem {Lycopodium complanatum), or square {L. tetragonum) ; 

 several resemble large Mosses {L. fontinaloides), or long cords {L. funiforme). 

 L. clavatum has often creeping , stems sometimes more than 13 feet long, and 



