IOWA ACADEMY OF SCIENCES. 
215 
on 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 their 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- 
latus, the seed gerpainating 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, 
