3^0 TRANS. ST. LOUIS ACAD. SCIErNCE. 



Clinton; at the head of Goat Island, Niagara, between stones, G. Engel- 

 mann; Oneida Lake, J. A. Paine; in Oswego river, F. Pursh, probably 

 (see p. 353). Massachusetts : Mystic Pond near its lower end, gregarious 

 m soft mud in i foot of water, also in other parts of the same pond, and in 

 Spot, Spy and Horn ponds, on sandy bottom, all near Boston, W.Boott; 

 Hammond's Pond, W. G. Farlo-ju ; Concord' brook, gregarious, on firm 

 bottom, H. Mann; Beaver Pond near Beverly, J. L. Russell; Uxbridge, 

 in Grafton Pond and several other ponds, /. W. Robbins. Vermont : Mt. 

 Mansfield, in the Lakeof the Clouds, C. G.Pringle, H. Mann, on gravelly 

 bottoms, I to 2 feet deep; Lake Dunmore, A. W. Chapnan. New°Hamp- 

 shire : Lake Winnipiseogee, in mud with Gratiola aurea, Eriocaulon, etc., 

 G. Engelmann (these specimens were the types of Durieu's /. Braunii),' 

 H.Mann, W. Boott ; Echo Lake in the Franconia Mountains (where Mr. 

 Tuckerman and myself had found I. lacnsiris), W. Boott. Maine : Moose 

 Lake on Kennebunk river, C. E. Smith. Nova Scotia, Shelburne, T. P. 

 James. Greenland, in the south, " Tessermint," /. Vahl (perhaps this is 

 the true /. eckinosfora; I could not well analyze the small and poor spe- 

 cimen in my possession;. Westward the species has been found in West- 

 ern Canada (Ontario) near Hastings and in a lake northeast of Belleville, 

 on a muddy bottom, J. Macoun. Michigan : Bellisle in Detroit river, H. 

 Gillman. Utah : Lake at the head of Bear river in the Uintah Mountains, 

 at 9,500 feet alt., 5. Watson; this is the most western and highest, quite 

 isolated, locality known to me. ' 



This form is most closely connected with the European type ; the leaves 

 are perhaps not quite so finely tapering; stomata can always be found, at 

 least near the tip of the leaf; the sporangia, white in the type, are spotted 

 with brown sclerenchym cells ; the macrospores I cannot distinguish either 

 m size or sculpture; the microspores I find a little smaller. I may state 

 here that the name of I. Braunii is preoccupied, as it has already been 

 given to one of the two species of the Tertiary deposits, the well marked 

 spores of which have been discovered in the German Brown Coal strata- 

 Prof Braun therefore proposed for our plant, if it should eventually be 

 considered distinct, the name of/, ambigua. 



Var. ROBUSTA, Engelm., similar to the last, but much stouter, with 25 to 

 70 leaves, 5 to S inches long, with abundant stomata all over their surface- 

 velum covering about one-half of the large, spotted sporangium; macro- 

 spores 0.36 to 0.55 mm. thick, with the sculpture of the last; microspores 

 the same as m last. 



In Lake Champlain, on the north end of Isle La Motte, on a firm sandy ■ 

 soil with silt, in I to 2 feet of water, C. G. Pringle. Larger and stouter 

 than any form of the last, but principally distinguished from it by the abun- 

 dance of stomata. -^ 



Var. BooTTii, Engelm. I. c. Leaves erect, soft, bright green, fewer (x2 

 to 20) short (4 to 5 inches long) ; stomata, mostly fe.' ne!r the t^ spo! 

 rangia nearly orbicular, pale-spotted, § or more covered by the broad 

 velum; macrospores 0.39 to 0.50 mm. thick, with longer and slenderer 



