THE AMPHIBIOUS QUILLWORTS. 241 



rcticiilata and Palincri, respectively, have been found. 

 It is a remarkable fact that hoctes riparia forms should 

 be found only at the head of Delaware Bay, and Isoetcs 

 saccliarata forms only in similar situations in a neighbour- 

 ing bay, especially since the two are so closely related. 

 It would seem as if the progeny of a single species 

 settling in the region have been modified by the sur- 

 roundings until they have assumed their present forms. 

 Mr. Eaton apparently considers that Isoetes saccJiarata is 

 represented in New England, since he has recently 

 described the variety Ainesii from Massachusetts. It 

 appears, however, better referred to hoctes Canadcnsis 

 Robbiiisii. 



Isoetes Foveo/ata. 



Whatever may be the status accorded this form, at 

 present, it is certainly closely related to Isoetcs Engel- 

 inaiini. The patterns of the markings on the mega- 

 spores are almost identical, but there is so much differ- 

 ence in the thickness of the reticulations that the spores 

 present a very different appearance. 



Isoetes foveolata is a stouter, shorter plant than Isoetes 

 Engclmanni, with from fifteen to sixty pinkish leaves two 

 to six inches long, bearing stomata 

 mostly near the tips. The peripheral 

 bast bundles are absent, and the spo- 

 rangia are thickly spotted with dark 

 cells which are often assembled into 

 groups. Some plants appear to bear 

 only megaspores. These are from 

 380 /* to 560* in diameter, flattened on 

 the hemisphere bearing the commis- 

 sures, and covered with reticulations so wide and so 



