146 NATURAL HISTORY BULLETIN. 



the minor morphological characters which determine 

 species or even genera, and accounts for the wide 

 difference between the extravagant genus-making of Fee, 

 Presl and John Smith, and the extreme conservatism of 

 many more recent English and American students of the 

 group. It is not purposed here to enter upon a general 

 discussion of the subject of nomenclature, nor indeed to 

 take up the discussion in detail with reference to this group. 

 The purpose of this paper is fully accomplished in the 

 recording of certain forms under names which will leave 

 no doubt of their identity, but as there are a few deviations 

 from the names now ordinarily recognized, some explana- 

 tion is desirable. 



So far as the larger subdivisions are concerned the 

 writer sees no reason for the abandonment of the names 

 applied by earlier writers to well-defined groups. For that 

 reason Willdenow's Gonopterides and Hydropterides, 

 elevated to the rank of classes, are here used. 



Willdenow* defined these groups in 1810, though he had 

 already made use of the names in the preceding yearf. 



The group Gonopterides was made to include the genus 

 Equisetum , and was well defined. 



The group Hydropterides included the class as used 

 here and the genus Isoetes. As the position of the latter is 

 still problematic, and as no specimens from Iowa are found 

 in the University herbarium, % no attempt is here made to 

 assign to it a definite place. It may be necessary to still 

 further subdivide the Hydropterides. The name St achy op- 



*Sp. Plantanim, vol. v, pp. xxxxi and xxxxii. 



fin Enumeratio Plantarum, pp. 1064-1076 (1809). 



%Isoetes melanopoda J. Gay was collected in Iowa by G. Vasey in 1862 

 (Botanical Works of Englemann, p. 452, foot-note), and was 

 reported from Clinton county by Prof. Arthur (Proc. Dav. Acad. 

 Sci., vol. iv, p. 67, 1886). All subsequent reports are based on these 

 records. 



