4 5 ISOETACEAE. 



x. Isoetes lacustris L. Lake Quillwort. (Fig. 102.) 



Isoetes lacustris L. Sp. PI. noo. i/53- 



Isoetes macrosfiora Durieu, Bull. Soc. Bot. France, 11: 

 101. 1864. 



Submerged or rarely above water in dry seasons ; 

 leaves 10-25, rigid, rather thick, scarcely tapering, 

 dark or olive green, obtusely quadrangular, 2'-6' 

 long ; stomata none ; peripheral bast-bundles want- 

 ing ; sporange orbicular or broadly elliptic, un- 

 spotted ; velum rather narrow ; ligule triangular, 

 short or somewhat elongated ; macrospores 500- 

 800 u in diameter, marked all over with distinct or 

 somewhat confluent crests, and bearing three con- 

 verging ridges ; microspores 35-46 // long, smooth. 



In i-5 of water, Labrador to the Northwest Terri- 

 tory, south to eastern Massachusetts and New Jersey. 

 Also in Europe and Asia. 



2. Isoetes Tuckermani A. Br. Tuckerman's Quillwort. (Fig. 103.) 



Isoetes Tuckermani A. Br. in A. Gray, Man. Ed. 5, 

 676. 1867. 



Submerged or rarely partly or wholly emersed 

 during very dry seasons ; leaves 10-30, very slen- 

 der, tapering, olive-green, quadrangular, 2 / ~3 / 

 long, without peripheral bast-bundles, the outer 

 recurved ; sporange oblong, mostly white, its upper 

 one-third covered by the velum ; macrospores 440- 

 560 n in diameter, with wavy somewhat parallel 

 and branching ridges on the upper half, separated 

 by the three converging ridges, the lower covered 

 with an irregular network ; microspores 26-32 ,u 

 long, nearly smooth. 



In ponds, Newfoundland to Middlesex county. Mass- 

 Q achusetts, clustered in shallow water. 



3. Isoetes echinospora Braunii (Durieu) Engelm. Braun s Quillwort. 



(Fig. 104.) 



Isoetes Braunii Durieu, Bull. Soc. Bot. France, n: 101. 

 1864. 



Isoetes ech inosfwra var. Braunii Engelm. in A. Gray, 

 Man. Ed. 5, 676. 1867. 



Submerged or in dry seasons emersed, leaves 12- 

 25, tapering, soft, reddish-green, 3 / -6 / long, with- 

 out peripheral bast-bundles, bearing stomata only 

 toward the tip ; sporange orbicular or broadly 

 elliptic, spotted, one-half to three-fourths covered 

 with the velum; macrospores 400-500^ in diameter, 

 covered with broad spinules which are often 

 slightly confluent and incised at the tips ; micro- 

 spores 26-30 n long, smooth. 



Labrador and Greenland to Alaska, south to New 

 Jersey, Pennsylvania and Utah. 





