20 FLORA. 



Family i. MARSILEACEAE R. Br. 



Perennial herbaceous plants rooting in mud, with slender creeping 

 rootstocks and 4-foliolate or filiform leaves. Asexual propagation consist- 

 ing of sporocarps borne on peduncles which rise from the rootstock near 

 the leaf-stalk or are consoiidated with it, containing both macrospores 

 and microspores. The macrospores germinate into prothallia which 

 bear archegonia, while the microspores grow into prothallia bearing 

 antheridia. Two genera and some 45 species of wide distribution. 



i. MARSILEA L. 



Marsh or aquatic plants, the leaves commonly floating on the surface of shallow 

 water, slender-petioled, 4-foliolate. Peduncles shorter than the petioles, arising 

 from their bases or more or less adnate to them. Sporocarps ovoid or bean- 

 shaped, composed of two vertical valves with several transverse compartments 

 (sori) in each valve. [Name in honor of Giovanni Marsigli, an Italian botanist, 

 who died about 1804.] About 40 species, widely distributed. 



Sporocarps glabrous and purple when mature. i. M, quadrifolia. 



Sporocarps densely covered with hair-like scales. 2. M. vestita. 



1. Marsilea quadrifolia L. EUROPEAN MARSILEA. (I. F. f. 73.) Root- 

 stock slender, buried in the muddy bottoms of shallow lakes or streams. Petioles 

 usually slender, 5-13 cm. high, or when submerged sometimes elongated to 3-6 

 dm. Leaflets mostly triangular-obovate, variable in outline, 6 16 mm. long, 412 

 mm. wide, glabrous or rarely with scattered hairs when young, the margins 

 entire ; sporocarps 2 or rarely 3 on a branching peduncle, which is attached to the 

 petiole at its base, covered with short yellowish-brown hairs when young, becom- 

 ing glabrous and dark purple when mature ; sori 8 or 9 in each valve. Along the 

 shores of Bantam Lake, Litchfield Co., Conn., whence it has been introduced into 

 various parts of the country, notably into E. Mass. Also in Europe and Asia. 



2. Marsilea vestita Hook & Grev. (I. F. f. 74.) Rootstock slender. Petioles 

 slender, 5-13 cm. high; leaflets similar to those of the preceding species, entire or 

 toothed ; sporocarps 4-8 mm. long, 4-6 mm. wide, with a short raphe, a short 

 and blunt lower tooth and an acute and sometimes curved upper one, densely 

 covered with soft spreading narrow hair-like scales, or (in the forms known as M. 

 mucronatd) these are short and appressed or almost wanting ; sori 6 n in each 

 valve. In wet sand or in shallow ditches, Kan. to Ariz, and Mex., north to Br. 

 Col. Also found in Fla. 



Family 2. SALVINIACEAE Reichenb. 



Small floating plants with a more or less elongated and sometimes 

 branching axis bearing apparently 2-ranked leaves. Sporocarps soft, 

 thin-walled, borne 2 or more on a common stalk, i -celled, with a central 

 often branched receptacle, which bears macrosporanges containing a 

 single macrospore or microsporanges containing numerous microspores. 

 The macrospores germinate into prothallia which bear archegones, the 

 microspores into prothallia which bear antherids. The family consists 

 of two genera. 



Leaves 12-18 mm. long, 2-ranked, on mostly simple stems. i. Salvinia. 



Leaves minute, closely imbricated on pinnately branching stems. 2. Azolla. 



i. SALVINIA Adans. 



Floating annual plants with slender stems bearing rather broad 2-ranked 

 leaves. Sporocarps globose, depressed, 9~i4-sulcate, membranous, arranged in 

 clusters, I or 2 of each cluster containing 10 or more sessile macrosporanges, each 

 containing few macrospores, the others containing numerous smaller globose 

 pedicelled microsporanges with very numerous microspores. Leaves rather dark 



