2 5 4 THE TERRESTRIAL QUILLWORTS. 



brown, 22 /* to 35 /* long. This form was found in the 

 vicinity of San Diego, California, and has since been dis- 

 covered in Lower California. It grows in the evanescent 

 pools mentioned as the habitat of Pilularia Americana, 

 and, like that plant, it disappears soon after the pools 

 dry up. When, through lack of winter rains, the pools 

 do not appear, the plants remain dormant sometimes for 

 two years or more in succession. 



Isoetes Minima. 



This diminutive species, with leaves from one to two 

 inches long, was collected by Suksdorf on a damp prairie 

 near Waverly, Washington, and has not been found else- 

 where. The leaves have the bast bun- 

 dles usual to terrestrial species, and the 

 indusium nearly covers the unspotted 

 sporangia. The megaspores are from 

 290^ to 35O/" in diameter, covered with 

 short, blunt, slender spinules that in ar- 

 rangement Suggest what WOuld result if Megasporeof 



Isoetes minima. 



the warts on the spores of other species 

 common to the same general region were elongated. 

 The equator is also set with these points, making it 

 " resemble a ship's wheel." This is, so far as known, 

 the smallest American species. 



