^Sz TKANS. ST. LOUIS ACAD. SCIENCE. 



B. Amphibious, partially emerged, submerg-edonly in the pearlier period of their 

 gro\vth or temporarily; stomata always present. 



* Without peripheral bast-bundies; intermediate between tlie sub- 

 merged and the truly amphibious species. 



I Velum partial. 



6. I. SACCiiARATA, Engelin. A small plant, usually with a flatj de- 

 pressed trunk; leaves subulate, olive-green, spreading, lo to 20 in number, 

 2 to 3 inches long; sporangium oblong, spotted, with a narrow velum; 

 ligula triangular; macrospores 0.40 to 0.47 mm. thick, covered with very 

 minute distinct or sometimes a little confluent warts; microspores papil- 

 lose, a.024 to 0.02S mm. long, — Gray Man. 1, c. 



On the banks of the "Wicomico, below Salisbury, and of the Nanticoke 

 rivers which empty into the Chesapeake Bay, eastern shore of Maryland, 

 above salt water, scattered on a thin stratum of mud covering a bed of 

 gravel, overflowed by the tides, in company with Sagittaria pusilla^ Rri- 

 ocaulon^ Tillaca simplex^ Micrantkemum Nuttallii^ etc., W, M. Canby, 

 The trunk is in this species unusually flat, about half as thick as it is wide 

 in the direction of the groove; about one inch of the base of the leaves is 

 pale, and covered with mud agitated by the tides, the upper part is olive- 

 green and when out of water apt to be borne down by mud ; stomata 

 abundant; macrospores as if sprinkled over with minute white grains of 

 sugar, whence the name* 



7. I. RiPARiA, Engelm. A larger plant with slender but rather rigid 

 deep green leaves (about 15 to 30 in number), 4 to 8 inches long, rarely 

 longer ; stomata numerous, dissepiments thick, consisting of about 4 layers 

 of cells; sporangia mostly oblong, distinctly spotted by groups of brown 

 sclerenchym cells, \ or rarely i of it covered by the velum; macrospores 

 among the largest, o 45 to 0.65 mm. in diam., marked with jagged crests 

 isolated, or anastomosizing, especially on the lower surface, which thus 

 becomes somewhat reticulated ; microspores more or less tuberculated, 

 0.02S to 0.032 mm. long.— Flora, Regensb. Mar. 31, 1846; Am. Jour. Arts 

 & Sci. 3, p. 52, 1847 : Gray Man. 1, c< 



On the banks of the lower Delaware river between the limits of the tides 

 in mud covering gravel, from Burlington, T, A. Conrad, to Wilmington, 

 W. M* Ca7ihy^ and especially about Philadelphia, where Nuttall first dis- 

 covered and W. S. Zanizinger^ E. Durand -xnd the later botanists have 

 abundantly collected it, associated with Elaiine, Limosella, Micranthe- 

 mum^ Sagittaria pHsilla^ etc. ; also in millponds and still parts of streams 

 in New England, Uxbridge, J. W. Rohhins, Brattleborough, C. C. Frosty 

 and northward, maturing in August and September. —Near /. lacustrisy 

 with leaves as dark green and almost as rigid, and with spores approach- 

 ing it in size and sculpture, but readily distinguished by its stomata and 

 ty the spots on the sporangium ; from /. eckinospora var, Braunii, with 

 which smaller forms it may possibly be confounded; it can always be 

 Icnown by the darker, stiffer leaves and especially by the character of the 

 «pores. Some of the Uxbridge specimeoB, entirely submerged 2 to 4 feet 



