=4° THE AMPHIBIOUS QUILLWORTS. 



The true Isoetcs riparia lias apparently nex'cr 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 Isoetcs riparia that it is now often 



- ''cy^;'>.'-^. suggested that they are two extreme 



^^■^dM^m." fo''''"s of the same species. Not only 



are t\-pical plants very much alike, but 



various intergrading forms have been 



found. Notwithstanding this, it Avill 



be retained as a species here, in order 



Megasporeof notto confuse the beginner, wlio will 



Isoetes saccharata. _ , . , . , 



nnd 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 550A 

 and appear "as if pprinl-;led with minute grains of white 

 sugar." They may be distinguished from those of 

 typical Isoetcs riparia by the markings being slenderer 

 and shorter, with a faint resemblance to those of Isoetcs 

 ccJiinospora. 



At present, typical plants of Isoetes saccharata have 

 been found only on tidal fiats 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 Gazette 

 for September, 1903. Two seasonal forms, named 



