IOWA ACADEMY OF SCIENCES. 215. 



Oil thistles, but it may be some time before I shall be able 

 to get together the manuscript lost in the fire. With this 

 apology 1 present these notes. I am especially indebted to 

 Dr. William Trelease and Dr. B. L. Robinson for kindly 

 allowing me to examine the material in their collections. 

 Prof. T. H. Macbride and Prof. B. Shimek have also kindly 

 permitted me to examine the material in the State Uni- 

 versity of Iowa. I am also indebted to Messrs. Reppert, 

 H. W. Norris, T. J. Fitzpatrick, and Cratty, for the privi- 

 lege of examining <-heir collections. The collections of the 

 State University and Mr. Reppert are quite full of Iowa 

 material, and contain a number of interesting forms. 1 

 am also indebted to Professor Selby and Professor Hitch- 

 cock, for material from their respective states, and Mr. 

 Miller, who was kind enough to look up some matters for 

 me with reference to thistles in the vicinity of Davenport. 

 I have followed Dr. Gray in his interpretation of the 

 genus, believing that the most logical one. 



ECOLOGICAL. 



Most of the thistles belong to that class of plants com- 

 monly called mesophytes, living in a climate and growing 

 in a soil supplied with sufficient moisture to produce good 

 agricultural crops. Thus it is that these plants are so com- 

 monly found on our prairies and in woods. A few of the 

 western species are xerophytic, being adapted to a dry 

 climate and a soil containing comparatively little moisture. 

 A few are semi-hydrophytic, growing in soil that is quite 

 moist, too moist for ordinary mesophytes. The Cnicus 

 muticus is the only representative of this society in Iowa. 

 The species are usually biennial, like the Cnicus lanceo- 

 latiis, the seed germinating in the spring and producing a 

 rosette of leaves. The rosette arrangement protects the 

 plant from cold in the winter and mechanical injuries. 

 The second season the plant sends up an erect stem that 

 bears the foliage, and during late summer, flowers. Some, 



