THE AMPHIBIOUS QUILLWORTS. 



23s 



Mej^aspore of 



Isoeifs En^elmanni 



Ca^'oliniana. 



species' range the spore-markings are less constant and 

 the species breaks up into varieties. The v^nety font a?ia, 

 distinguished from the type by having many stomata, four 

 or more peripheral bast bundles, and a spotted sporan- 

 gium, has been reported from eastern Pennsylvania. A 

 very slender form, with about 'a dozen 

 leaves, often found with the t)pe, is 

 named variety gracilis. It is probably 

 due to plants growing in deep water or 

 in dense shade. The variety Gcorgiana 

 has few leaves and slightly larger mega- 

 spores. More pronounced is the form 

 from North Carolina described as 

 Isoetcs Ejigebnaniii Caroliniana. In 

 this the leaves and indusium are slightly broader, and 

 the megaspores are marked by thin and broken crests 

 which often present spinules like those of Isoetes echino- 

 spora and have few if any reticulations. The microspores 

 also are slightly larger and densely spinulose. 



Isoetes Engcbnanni is found most abundantly on the 

 gravelly shores of rivers and streams. Eaton says that 

 in New England it is very common in clay soil in 

 ponds and ditches, but rarely occurs in mud and sand. 

 In parts of New Hampshire it is reported as common in 

 nearly every millpond and ditch with a clay bottom. It 

 is likely that the plants growing in ponds are seldom 

 above water, which shows how arbitrarily the amphibi- 

 ous group of quillworts has been constituted. The 

 species ranges from Maine to Delaware, Pennsylvania, and 

 Missouri. The variety Gcorgiana is found only in the 

 State for which it is named. Isoetes Engelnianni Carolin- 

 iana has been found in several localities in North Caro- 

 lina. 



