THE TERRESTRIAL QUILLWORTS. 



ceptable to it, at least so far as the production of fruit 

 is concerned, for it has been found that, when covered 

 with water, the leaves last through the season, though 

 spores are seldom produced. 



The leaves of this species are from fifteen to sixty in 

 number, slender, erect, and from six inches to a foot 

 long. They are usually black and shining at base; hence 

 the specific name. As in all the species that are exposed 

 for a considerable time to the air, the leaves possess 

 stout peripheral bast bundles which 

 aid in holding them erect. The indu- 

 sium is very narrow or sometimes ab- 

 sent, and the sporangium is spotted. 

 The megaspores are usually small, but 

 vary in size, averaging from 250*" to 

 4OO/" in diameter. They have broad, 

 low commissures and are marked with 

 indistinct dots and low vermiform wrinkles. Except for 

 the fact that they are not dark coloured, they have a 

 close resemblance to those of Isoetes melanospora. The 

 microspores are spinulose. The megaspores and micro- 

 spores are usually borne on separate plants. 



As the water in its habitat disappears, the leaves be- 

 gin to shrivel, and soon little holes are left in the soil 

 at the bottom of which are the bulbs and sporangia. 

 With the renewal of moisture the spores and the parts 

 surrounding them rise and float away, to form new colo- 

 nies. This species is found from Illinois, Iowa, and Ne- 

 braska to Texas, and it also has a variety in California 

 which differs in having smooth megaspores and larger 

 microspores. In some parts of its range, Isoetes melano- 

 poda is abundant, but it is not evenly distributed, being 

 often rare or absent. In Texas a larger plant with pale 



Megaspore of 

 Isoetes melanopoda. 



