THE AQUATIC QUILLWORTS. 



225 



times to root them up. The fleshy corms or rootstocks 

 have occasionally been eaten in Europe, but are said to 

 have an earthy taste that is scarcely palatable. The 

 American range of this species is given as from New 

 Jersey, Lake Superior, Colorado, and California north- 

 ward. The plant originally described by Engelmann as 

 Isoetes lacustris, vz.n&ty paiipercula, is considered by Mr. 

 Eaton as entitled to specific rank. It has fewer, thinner, 

 and shorter leaves and smaller spores. It is found in 

 Colorado and California. This form was also collected 

 by Henderson, who named it Isoetes occidentalis. 



T'uckerman s ^uiilwori. 



In Tuckerman's quiWwoYt {Isoetes Tnckerniani) we have 

 a plant with much the habit of Braun's quillwort, but 

 with spore characters that link it more closely with 

 Isoetes lacustris and Isoetes riparia. It may be distin- 

 guished at sight, however, by the 

 leaves, which are very slender and 

 tinged with red. They are from two 

 to five inches long and usually spirally 

 twisted. It was long thought that this 

 species lacks stomata, but it is now 

 known occasionally to bear them 

 in small numbers, especially if grow- 

 ing in situations where they may be 

 exposed to the air. The sporangia are small, sparingly 

 pale spotted, and the upper third is covered by the in- 

 dusium. The megaspores are 450/* to 560/' in diameter, 

 marked with parallel and anastomosing ridges on the 

 upper segments, and somewhat more reticulated below. 



Megai^pore of 

 Isoetes Tuckeriitani. 



