1 46 NATURAL HISTORY BULLETIN. 



Morong, Naiad. X. A., 41; Wats, and Coult., Gray's Man., 

 6th ed., 563; Upham, Fl. Minn., 137. 



A graceful little plant with delicate, bright foliage, some- 

 what resembling P. -pus ill us but larger. Rare in America. 

 Ponds and shallow lakes. July. 



Iowa Lake, Emmet county, C ratty ; Muscatine, Herb. 

 Reppert) JVb. y^.6 in part ; Spirit Lake, Hitchcock. 



12. P. pusillus Linn. Spec. PL, 127 (1753). 



Morong, Xaiad. N. A., 45; Wats, and Coult., Gray's Man,, 

 6th ed., 563: Macmillan, Metas. Minn. Yak, 36; Hitchcock, 

 Ames FL, 522. 



A delicate species preferring shallow ponds and lakes. July. 



Ames, abundant at Cairo Lake, Hitchcock; Muscatine, 

 Herb. Reppert. jVo. J 4.6 in part. 



13. P. spirillus Tack. Am. Jour. Sci. and Arts, 2nd Ser., 

 VI , 226 (1848). 



Morong, Xaiad. X. A., 49; Wats, and Coult., Gray's Man., 

 6th ed., 560; Beal and Wheeler, FL Mich., 145; Bot. Death 

 Val. Ex., 210. 



This interesting little plant, not before reported from the 

 State, was collected in August, 1889, at Carnsforth, Iowa, by 

 Prof. Hitchcock, and again in July, 1894, by Mr. Kenneth 

 McKenzie in ponds along the C, R. I. & P. R. R., between 

 Muscatine and Fruitland. The specimens approach P. diver- 

 sifolias Raf. [P. hybridus Michx.) in some characters, but are 

 quite clearly distinguished by the submerged spikes being 

 sessile or nearly so; by the broader submerged leaves, and by 

 the curious snail-like fruit which shows the coiled embryo 

 very conspicuously, even in the dried specimen. 



14. P. pectinatus Linn. Spec. PL, 127 (1753). 



Morong, Xaiad. X T . A., 51; Wats and Coult., Gray's Man., 

 6th ed., 564; Macmillan. Metas. Minn. Val., 35; Arthur, Fl. 

 Iowa, 30. 



