226 THE AQUATIC QUILLWORTS. 



In New Hampshire, Mr. Eaton has discovered plants in 

 which the spores were of various diameters up to 750 /* 

 but otherwise like the type. The microspores are 

 smooth and 26 / to 32^ long. 



So far as known, Tuckerman's quillwort is confined to 

 the New England States. It was formerly considered 

 rare, but a more careful study of the material has shown 

 that much of what was once referred to Isoctes lacustris 

 and Isoctes riparia really belong to this species. Mr. A. 

 A. Eaton asserts that within its range it is likely to 

 occur in any large pond with sandy shores, especially if 

 a little silt has been deposited upon the sand. It grows 

 in from one to four feet of water, forming extensive 

 colonies, and is rarely found in situations where the 

 water is not at least a foot deep during the drouths of 

 summer. The depth at which it grows suggests the 

 possibility that the red colouring-matter in the leaves 

 may aid in assimilation, just as the same colour is known 

 to do in the red seaweeds. 



Plants from Maine and New Hampshire, in which the 

 leaves are longer and stouter, have been named the 

 variety borealis. This is said to have enough likeness to 

 plants of Isoetes lacustris to be almost entitled to rank 

 as a form of that species. Still another form, described 

 as Isoetes Harvey 7, has recently been found in Maine. In 

 this the leaves are stout and very numerous, often one 

 hundred or more, though less than three inches in 

 length. The sporangia are small, unspotted, and about 

 one-third indusiate. The megaspores are 525 /" to 650^ 

 in diameter, but may occasionally be found of diameters 

 up to 800 I L . The spores are similar to those of typical 

 Tuckermani) but the leaves are very different. In the 

 opinion of the describer, however, it is not sufficiently 



