2 4 o THE AMPHIBIOUS QUILLWORTS. 



Tlic true Isoctcs riparia has apparently never been 

 found anywhere except along the lower Delaware, 

 though often reported from other localities. 



Isoetes Saccharata. 



This was formerly supposed to be a distinct species, 

 but additional collections and further study have shown 

 it to be so nearly like Isoetes riparia that it is now often 

 suggested that they are two extreme 

 forms of the same species. Not only 

 are typical plants very much alike, but 

 various intergrading forms have been 

 found. Notwithstanding this, it will 

 be retained as a species here, in order 

 Megasporeof not to confuse the beginner, who will 



Isoetes saccharata. r . . 1-1 11 



find it so treated in the text-books. 



The leaves are from ten to twenty in number, dark 

 green, slender, and from two to five inches long. They 

 have no bast bundles, and the stomata are abundant. 

 The indusium is narrow, and the sporangium spotted. 

 In diameter the megaspores measure from 400 /" to 550^ 

 and appear " as if sprinkled with minute grains of white 

 sugar." They may be distinguished from those of 

 typical Isoetes riparia by the markings being slenderer 

 and shorter, with a faint resemblance to those of Isoetes 

 ecJiinospora. 



At present, typical plants of Isoetes saeeJiarata have 

 been found only on tidal flats about the head of Chesa- 

 peake Bay and the rivers that empty into it. A com- 

 plete list of the stations, with a map and discussion of 

 its distribution, was published in the Botanical Gazcttr 

 for September, 1903. Two seasonal forms, named 



