SAIJ^INIACEM. 127 



ing peduncle, 3 — 4-celled ; macrospores 13 — 17 in each cell, 

 not constricted in the middle. Santa Barbara, California 

 (Mrs. Cooper), Arkansas {Nuitall), Oregon {Leiberg). 



ORDER III. SALVINIACEiE. 



Floating plants with a more or less elongate and sometimes 

 branching axis bearing apparently distichous leaves. Sporo- 

 carps soft, thin-walled, two or more on a common stalk, i-celled, 

 with a central, often branched receptacle which bears macro- 

 sporangia containing a single macrospore, or microsporangia 

 containing numerous microspores. Consists of the two follow- 

 ing genera. 



I. Salvinia Schreb. Leaves 6" — 9" long, with a distinct 

 midrib. 



II. Azolla Lam. Leaves miimte, numerous, closely imbri- 

 cate, deeply lobed. 



I. SALVINIA Schreb. 



Floating annuals with slender stems bearing small two- 

 ranked leaves. Sporocarps arranged in clusters, globose, mem- 

 branous, I — 2 of each cluster containing 10 or more macro- 

 sporangia, the others containing numerous smaller microspo- 

 rangia. Named for Sahn'm\ a Florentine professor. Contains 

 thirteen species, one of which is found with us. 



I. S. natans Hoffni. Leaves oblong, horizontal, rounded 

 or slightly cordate at base, ^' — i' long, bright green above, the 

 under surface matted with brown, pellucid hairs ; sporocarps 

 4 — 8 in a cluster. {Marsi'h'a natans L.) Bois Brule Bottoms, 

 Perry County, Missouri {Demefrz'o.) Reported by Pursh from 

 Central New York ; the exact station unknoA^n. 



IL AZOLLA Lam. 



Small, moss-like plants with pinnately branched stems cov- 

 ered with minute, imbricate, 2-lobed leaves, and emitting rootlets 

 beneath. Sporocarps of two kinds, borne in the axils of the 

 leaves. Smaller sporocarps ovoid, containing a single macro- 

 spore at the base. Larger sporocarps globose, producing from 

 the base many pedicelled sporangia, containing several masses 



