23S. 



THE AMPHIBIOUS QUILLWORTS. 



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

 tain tjiat this is a separate species it is therefore properly 

 called Isoctes Canadensis. For some time, however, the 

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

 In appearance Isoctes Canadensis is much like Isoetes 

 Engelnianni. The Iciives are fiom 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 

 mcgaspores 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- 

 ance the spores suggest the spores of 

 Isoetes Engcbnanni, in ^vhich the crests 

 have so nearly disappeared that vestiges of only the 

 heaviest- remain. The microspores are 22 a 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, Amesii, of 

 Isoetes saccharata, 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 Isoetes riparia or 



Megaspore of 

 Isoetes Canadensis. 



