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IOWA ACADEMY OF SCIENCE 



It is not likely that Chenopodium can hold its own against 

 this army; Ambrosia has the same advantage of fecundity and 

 early germination of seed. Whether Lactuca also will be swept 

 down remains to be seen. It will be an interesting fight. 



NEW SPECIES APPEARING DURING THE SEASON OF 1915. 



Equisetum arvense. 

 Elymus robustus. 

 Sisymbrium officinale. 

 Polygonum aviculare. 

 Polygonum erectum. 

 Salsola Tragus. 

 Lepidium virginicum. 



Potentilla monspeliensis. 

 Trifolium repens. 

 Verbena hastata. 

 Erigeron canadensis. 

 Antbemis Cotula. 

 Artemisia biennis. 

 Lactuca scariola. 



Botanical Laboratory, 

 Grinnell College. 



