IOWA ACADEMY OF SCIENCES. 
205 
20. P. p erfoliatus richardsonii A. Bennett. (P. perfo- 
liatus lanceolatus Robbins.) Common in lakes and 
quite variable; a most beautiful species. 
21. P. zostercefolius Schum. Iowa Lake. 
22. P. foliosus Raf. (P. pauciflorus Pursh.) Common 
in lakes and slow streams. 
23. P. foliosus niagarensis (Tuck.) Morong. Swift 
running water below mill-dam, Estherville, Aug. 
7,1897. 
24. P. friesii Ruprecht. (P. major (Fries) Morong.) 
Iowa Lake, and probably in other lakes through- 
out the region. 
25. P. pedinatus L. Very common in lakes through- 
out this and adjoining counties. 
Naias L. 
26. N. flexilis (Willd.) Rost & Schmidt. Common in 
shallow water in lakes. 
SCHEUCHZERIACE^E. 
Triglochin L. 
27. T. maritimum L. Rare in marshes. Ours is the 
var elatum of Gray’s Manual.. 
ScHEUCHZERIA L. 
28. S. palustris L. Very rare; bog three miles north- 
west of Armstrong; the only known locality in 
the state. 
ALISMACEAS. 
Alisma L. Water-plantain. 
29. A. plantago-aquatica L. Very common in low ground. 
Sagittaria L. Arrow-head. 
30. S. latifolia Willd. (S. variabilis Engelm.) Frequent 
throughout but much less common than the next. 
31. S. ari folia Nutt. Very common in bogs and low 
places. This and the preceding species present 
great variation in leaf forms. 
