SALVINIACEAE. 



VOL. I. 



i. Salvinia natans (L.) Hoffm. Salvinia. 

 Floating Moss. Fig. 87. 



Marsilea natans L. Sp. PI. 1099. 1753. 

 Salvinia natans Hoffm. Deutschl. Fl. 2 : 



1795- 



Leaves oblong, rather thick, obtuse or emarginate 

 at the apex, rounded or cordate at the base, entire., 

 spreading, 6'-i2 r long, pinnately veined, bright green 

 and papillose above, the lower surface densely matted 

 with pellucid brown hairs; spordcarps 4-8 in a clus- 

 ter, the upper ones containing about 10 megaspo- 

 ranges, each containing a single megaspore, the re- 

 mainder containing numerous microsporanges each 

 with numerous microspores ; megaspores marked 

 with 3 obtuse lobes, these meeting at the apex. 



Bois Brule Bottoms, Perry Co., Missouri, and near 

 Minneapolis, Minn. Introduced into ponds on Staten 

 Island, N. Y. Reported by Pursh in 1814 from central 

 Xew York, but his exact station is unknown. Widely 

 distributed in Europe and Asia. 



2. AZOLLA Lam. Encycl. i : 343. 1783. 



Minute moss-like reddish or green floating plants, with pinnately branched stems covered 

 with minute imbricated 2-lobed leaves, and emitting rootlets beneath. Sporocarps of two 

 kinds borne in the axils of the leaves, the smaller ovoid or acorn-shaped, containing a single 

 megaspore at the base and a few corpuscles above it whose character is not fully known, 

 the larger globose, producing many pedicelled sporanges, each containing several masses of 

 microspores which are often beset with a series of anchor-like processes of unknown func- 

 tion. [Greek, signifying killed by drought.] 



About 5 species of wide geographic distribution. 

 Type species : Azolla filiculoides Lam. 



i. Azolla caroliniana Willd. Carolina 

 Azolla. Fig. 88. 



Azolla caroliniana Willd. Sp. PI. 5: 541. 1810. 



Plants greenish or reddish, deltoid or triangular- 

 ovate in outline, pinnately branching, sometimes 

 covering large surfaces of water. Leaves with 

 ovate lobes, their color varying somewhat with 

 the amount of direct sunlight, the lower usually 

 reddish, the upper green with a reddish border. 

 Megaspores minutely granulate, with three acces- 

 sory corpuscles; masses of microspores armed 

 with rigid septate processes. 



Floating on still water, Ontario and Massachusetts 

 to British Columbia, south to Florida, Arizona and 

 Mexico. Also in tropical America. Naturalized 

 in lakes on Staten Island, N. Y. 



Family 8. EQUISETACEAE Michx. 

 Fl. Bor. Am. 2: 281. 1803. 



HORSETAIL FAMILY. 



Rush-like perennial plants, with mostly hollow jointed simple or often much- 

 branched grooved stems, provided with a double series of cavities and usually 

 with a large central one, the branches verticillate, the nodes provided with dia- 

 phragms. Rootstocks subterranean. Leaves reduced to sheaths at the joints, 

 the sheaths toothed. Sporanges i-celled, clustered underneath the scales of ter- 

 minal cone-like spikes. Spores all of the same size and shape, furnished with 2 

 narrow strap-like appendages attached at the middle, coiling around the spore 

 when moist and spreading when dry and mature, in the form of a cross (elaters). 

 Epidermis impregnated with silica, rough. Prothallium on the surface of the 

 ground, green, usually dioecious. 



The family consists of the following genus: 



