100 
IOWA ACADEMY OF SCIENCES. 
P. lapathifolium L. Wet ground, frequent. 
P. pennsylvanicum L. Moist ground, common. 
P. muhlenlDeTgii Watson. Swamps, rare. 
P. orientate L. Escaped. Dr. C. C. Parker, coll. 
P. persicaria L. Waste ground, frequent. 
P. liydropiperoides Michx. Wet ground, infrequent. 
P. hydropiper L. Moist ground, infrequent. 
P. acre H B K Wet ground, common. 
P. virginianum L. Rich woods, common. 
P. sagittatum L. Moist ground, frequent. 
P. convolvulus L. Waste ground and fields, common. 
P. dumetorum L., var., scandens Gray. Moist thickets, 
infrequent. 
Fagopyrum esculentum Moench. Occasionally escaped. 
ARISTOLOCHIACE^. 
Asarum canadense L. Wooded hillsides, frequent. 
THYMEL^ACE^. 
Dirca palustris L. Dry prairies, common. 
SANTALACE^. 
Gomandra umbellata Nutt. 
EUPHORBIACE^. 
Euphorbia serpyllifolia Pers. Waste ground, frequent. 
Seems to run into E. glyptosperma Engelm. 
E. maculata L. Waste ground, common and variable. 
E. preslii Guss, Waste ground, infrequent. 
E. corollata L. Prairies and open woods, common. 
E. heterophylla L. Rocky river banks, rare. 
E. cyparissias L. Rarely escaped. 
Acolypha virginica L. Waste ground, common. 
URTICACE^. 
Ulmus fulva Michx. Woods, frequent. 
U. americana L. Low woods along streams, frequent. 
U. racemosa Thomas. Several trees known in one place in 
low woods. 
Celtis occidentalis L. Open woods along the Volga river, 
infrequent. 
Cannabis saliva L. Waste ground, frequent. 
Humulus lupulus L. Open woods, infrequent. 
TJrtica gracilis Ait. Moist ground, frequent. 
