TWO NEW ISOETES 



By A. A. Eaton. 



INCE the time of Engelmann there has accumulated in differ- 



ent herbaria a large amount of Isoetes material which has 



not been properly segregated. Through the kindness of 

 Prof. J. Macoun, of Ottawa, I received a long time since a lot of 

 interesting specimens collected in various places on the west coast 

 of America. Two at least of these are new; the one under con- 

 sideration at present being collected by Prof. J. M. Macoun, of 

 of the British Behring Sea Commission, on the side of an extinct 

 volcano on the island of Atka, near the western limit of the 

 Aleutian chain. 



It was entirely submersed in pools fed by springs, which ap- 

 parently are never low enough for any of the plants to become 

 emersed. Their appearance bears out this observation. The 

 round leaves, few stomata, large cells and broad dissepiments, as 

 well as absence of bast-bundles, place it among the submersed 

 species. It is described as follows: 



Isoetes Macounii, n. sp. Species small, submersed, with 

 aspect of lacustris. Trunk flat or slightly bilobed, .5-icm. broad. 

 Leaves, 5-12; 2-4.50111. long, very stout, 1-1.5™. wide, acuminate, 

 sparingly stomatose near the tip, reddish green. Dissepiments 

 5-6 cells wide, and walls of leaves 3-4. Bast-bundles absent. 

 Base of leaves widely winged. Ligula triangular-lanceolate. 

 Sporangium orbicular, 2.5-3^111. in diameter, indusiate, 

 thickly pale spotted. Macrospores 300-570//, average 450//, loosely 

 beset with very stout, short, blunt or confluent refuse spinules, 

 those below shading off to small papillae next the equator, while 

 those above grow on the commissures. Microspores averaging 

 35x27.4//, sometimes reaching 40 or 44//, finely and densely papil- 

 lose, or rarely blunt tuberculate, elliptical. Habitat, pools on an 

 extinct volcano, apparently never out of water, Atka, I. ; 52 N., 

 175 W., August 26, 1 891. J. M. Macoun, collector. 



A few of the microspores are densely covered with small 

 tubercles or papillse, and are even cristate. As the plants are 

 rather under-ripe, this may be the full -developed form. The 

 leaves have peculiar organs situated under the epidermis, which 

 might easily be mistaken for stomata. They are large, broadly 

 elliptical, with indurate edge and granular interior. In the many 

 American and European plants examined I have found them else- 



