42 MISC. PUBLICATION 4 2 3, U. S. DEPT. OF AGRICULTURE 



3. MARSILEACEAE. Pepper wort family 



Aquatic or semiaquatic, perennial plants with long-creeping, 

 branched, hairy rhizomes, rooting in mud; leaves in 2 rows, circinate 

 in bud, herbaceous, the long-stipitate blades 4-foliolate, cloverlike; 

 sporocarps borne at base of stipe, large, bony, 2-celled vertically,' 

 containing both megaspores and microspores. 



1. MARSILEA. Pepperwort 



1. Marsilea vestita Hook, and Grev., Icon. Fil. 2: 159. 1831. 



Prescott, Yavapai County, about 5,000 feet, in a pond {Kearney 

 and Peebles 12784), and near Fort Huachuca (Lemmon 2896). South 

 Dakota to British Columbia, south to Oklahoma, Texas, New Mexico, 

 Arizona, southern California, and Mexico; naturalized in Florida. 



4. AZOLLACEAE. Azolla family 



Fugacious, very small, floating, mosslike plants, the stems bearing 

 roots below; leaves minute, green or reddish green, borne alternately 

 in 2 rows upon short branches, deeply bilobed, the lower lobe sub- 

 mersed; sori completely indusiate, borne in pairs on the submersed 

 lobes, one acorn-shaped, containing a single megasporangium, the 

 other globose, containing numerous microsporangia. 



1. AZOLLA 

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



Camp Lowell, near Tucson, Pima County, in running water (Roth- 

 rock 714). New York to Alaska, south to Florida, Arizona, and 

 California; tropical America; sporadic, perhaps owing to escape from 

 cultivation. 



Mosquito-fern. 



5. ISOETACEAE. Quill wort family 



Small, submersed or partially emersed plants of ponds, streams, or 

 moist depressions; stems short, cormlike, crowned by numerous 

 crowded, subulate, inflated leaves; sporangia axillary, borne within 

 the enlarged hollow leaf bases, producing large subspherical mega- 

 spores and very numerous, powdery, angled microspores. 



1. ISOETES. Quillwort 



1. Isoetes bolanderi Engelm., Amer. Nat. 8: 214. 1874. 



In a small lake about 2 miles east of Tunnel Road, Black Mesa 

 Forest Reserve {Coville 1053). Mountain ponds and lakes, British 

 Columbia to Wyoming, Colorado, Arizona, and California. 



The var. pygmaea (Engelm.) Clute (Isoetes pygmaea Engelm.) was 

 collected in the Huachuca Mountains by Lemmon; known otherwise 

 only from Mono Pass, Calif., and Walker Lake, Nev. It differs from 

 the typical form of the species in its stouter and somewhat shorter 

 leaves. 



6. EQUISETACEAE. Horsetail family 



Rushlike plants of low places, the rhizomes perennial, wide-creeping; 

 stems mostly erect, cylindric, fluted, siliceous, simple or with whorled 



