250 THE TERRESTRIAL QUILLWORTS. 



a resting condition. The spores of all are very much 

 alike and show a regular gradation from one extreme 

 to the other. Evidently all the species are closely related. 



Isoetes Melanopoda. 



One of the best-known of the terrestrial species is 

 Isoetes Melanopoda, which was first discovered in Illinois 

 and appears to be peculiar to the prairie region extend- 

 ing from that State southwestward. It is often found in 

 alkaline flats, and its behaviour there is described as 

 follows : 



" Many of the wells and springs running into or passing through this 

 clay are damaged or sometimes rendered unfit for use by the quanti- 

 ties of sulphates of magnesia and soda entering into solution there 

 from. Occasionally this clay rises to the surface, forming low level 

 places which are popularly known as alkaline flats. During winter 

 and spring, while the rainy weather lasts, the flats, owing to their 

 level surface and imperfect drainage, are very wet, but by or before 

 the first of July, when the dry summer has well begun, they have be- 

 come the driest of all dry places, for the clay prevented the water from 

 soaking in, and the soil is so thin that an adequate store of moisture 

 could not be laid up. These flats are the home of Isoetes Butterz. 

 There are occasional basins in the flats which contain more or less 

 water, and here Isoetes melanopoda grows. It also occurs in nearly 

 all ponds, ditches, and wet-weather streams. It is more common 

 than the other, or at least it appears so, and it is so much easier to 

 find, owing to its greater size and paucity of companions. It disap- 

 pears in August." 



From this it will be seen that this plant is scarcely a dry- 

 ground species, though Underwood so lists it. Baker 

 places it among the amphibious species. It is found in 

 damp sands, however, and has been collected in a water- 

 melon patch. A certain amount of dryness seems ac- 



