202 
IOWA ACADEMY OF SCIENCES. 
123. C. vulpinoidea Michx. Wet ground; abundant. 
124. C. xanthocarpa^iok. Meadows; scarce. Not quite 
typical, as the perigynia are dark brown and 
distinctly nerved. 
125. G. sartwellii Dew. Wet meadows and bogs; 
frequent. 
126. C. rosea Schk. Common in woods and thickets. 
127. C. sparganioides Muhl .High woods; infrequent. 
128. C. scoparia Dry, open ground; common. 
129. C. cristatella Brit. (C. trihuloides cristata Bail.) 
Meadows; frequent. 
130. C. festucacea Willd. {C, straminea hrevior Dew.) 
Meadows and thickets; frequent. 
ARACE^. 
ArIStEMA. 
131. A. triphyllum (L.) Torr. Woods; common. 
132. A. dracontium (L.) Schott. Moist woods; frequent. 
Acorus. 
133. A. calamus L. Common in swamps. 
LEM NAG E^. 
Spirodela. 
134. S. polijrhiza (L.) Schleid. Common in ponds. 
Lemna. 
135. L. trisulca L. Common, with the preceding. 
COMMELINACE^. 
Tradesoantia. 
136. T, virginica L. Common in waste ground. 
PONTEDERIACE^. 
Pontederia. 
137. P. cordatah. Borders of ponds; local. 
Heteranthera. 
138. H, duhia (Jacq.) MacM. [R. graminea Vahl.) 
Ponds and muddy shores; infrequent. 
