238 THE AMPHIBIOUS QUILLWORTS. 



to the plant of course holds good, and since it seems cer- 

 tain that this is a separate species it is therefore properly 

 called Isoetcs Canadensis. For some time, however, the 

 name of Isoetes Dodgci is the one it has. commonly borne. 

 In appearance Isoetcs Canadensis is much like Isoetes 

 Engclineinni. The leaves are from eight to fifteen inches 

 long, often seventy-five in number, and when under 

 water are half erect and inclined to twist. The leaves 

 that appear in summer are shorter, as usual. The spor- 

 angia are about one fourth indusiate and spotted. The 

 megaspores are 500" to 675," in diameter, with irregular, 

 low, sub-continuous, thin crests scat- 

 ered over them. The hemisphere that 

 bears the commissures is decidedly 

 flattened, and the commissures them- 

 selves are inclined to produce thin, 

 short, lateral projections. In appear- 

 Megasporeof ance the spores suggest the spores of 



Isoetes Canadensis. 



have so nearly disappeared that vestiges of only the 

 heaviest remain. The microspores are 22 <" to 40" long, 

 ashy in colour, and wrinkled. 



Mr. Eaton has described a variety of this species from 

 Massachusetts, in which the leaves contain four bast 

 bundles and are rather stiff and erect, even when out of 

 the water. To this the varietal name of Robbinsii has 

 been given. The megaspores are described as being 

 thickly beset with anastomosing jagged walls, much as in 

 Isoetes riparia, though thicker. A variety, Amcsii, of 

 Isoetes saccliarata, appears to be enough like Robbinsii to 

 be classed with it. So intermediate are the characters 

 that distinguish Robbinsii that it might with equal pro- 

 priety be regarded as a variety of Isoetcs riparia or 



