MARSILIA FAMILY 1051 



or bean-shaped, usually with 2 teeth near the base, divided vertically into two 

 ceUs, which are subdivided into transverse compartments (sori). 



Sporocarps -with two distinct acute teeth separated by a rounded sinus, the upper tooth 

 the longer, straight or curved. 1. M. vestita. 



Sporocarps with the lower tooth short and blunt, the upper a mere rounded papilla or 

 wanting. 2. M. oligospora. 



1. M. vestita Hook. & Grev. Petioles 1-14 cm. long; leaflets broadly cun- 

 eate, usually hairy, entire; peduncles erect or ascending, distinct from the peti- 

 oles, scarcely as long as the sporocarps; sporocarps sohtary, hairy, with about 

 7-9 sori in each cell. B.C.— "la."— Ark.— Cahf. 



2. M. oligospora Goodding. Petioles 1-12 cm. long; leaflets cuneate, spread- 

 ing above, hairy or glabrescent; pedimcles erect or ascending, each united at 

 base with the base of a petiole, 0.4-1.7 cm. long; sporocarps sohtarj^ somewhat 

 deflexed, with 5-8 sori in each cell, clothed with lance-shaped, jointed, tubercu- 

 late hairs. Wyo. — Wash.; CaUf. 



Family 4. SALVINIACEAE. Salvinia Family. 



Aquatic, floating plants, bearing minute, apparentl}^ 2-ranked leaves on 

 a more or less elongate, sometimes branching, axis. Sporocarps borne 2 or 

 more on a common stalk, soft, one-celled, thin-walled, each containing a 

 central often branched receptacle, which bears either macrosporangia con- 

 taining solitary macrospores or microsporangia containing numerous micro- 

 spores. 



1. AZOLLA Lam. 



Small moss-like plants, with pinnately branched stems bearing rootlets on 

 the under side. Leaves imbricate, 2-lobed. Sporocarps borne in pairs beneath 

 the stem, some small, ovoid or acorn-shaped, containing at base a single macro- 

 spore with a few attached bodies of uncertain function above it, the others larger, 

 globose, containing on a basal placenta numerous stalked microsporangia enclos- 

 ing masses of microspores, which are usually fui-nished with anchor-shaped pro- 

 cesses. 



1. A. caroliniana Willd. Plants much branched, 6-25 mm. broad; lobes of 

 leaves ovate, the lower reddish, the upper green, reddish margined; macrospores 

 minutely granular, accompanied with three corpuscles; processes of the micro- 

 spores rigid, septate. In still waters: ''Ont." — "Fla." — Calif. — B.C.; trop. Am. 



Family o. EQUISETACEAE. Horsetail Family. 



Rush-like, verticillately branched or unbranched plants, with rootstocks 

 and mostly hollow, jointed stems, bearing sheaths at the nodes. Spores in 

 a terminal cone formed of verticels of stalked peltate bracts bearing on the 

 under side 6 or 7 sporanges, which open on the inner side. Prothallium in 

 damp places, green, variously lobed. 



1. EQUISETUM. Horsetail. 

 Characters of the family. 



Stem annual; spike rounded at the top; stomata scattered in the grooves of the stem. 

 Stems of two kinds, the fertile ones succulent, appearing earUer than the sterUe ones. 

 Fertile stems simple, soon withering, branchless. 1. E. arvense. 



Fertile stems, when older, producing branches, only the naked apex withering. 

 Branches compound ; ridges ■with 2 rows of hooked spinules. 



2. E. sylvaticum. 

 Branches simple; ridges with 3 rows of broad spinules. 3. E. pratense. 



Stems of one kind ; branches simple or none. 



Teeth of the sheaths persistent ; plant usually branched, at least in age. 



Sheaths loose; teeth grooved, black with white margins; central cavity one- 

 sixth of the diameter of the stem. 4. E. palustre. 



