8 ILLINOIS BIOLOGICAL MONOGRAPHS [98 



ACKNOWLEDGMENTS 



I am especially indebted to Professor William Trelease for his invalu- 

 able advice and criticisms throughout the course of the work. It was 

 at his suggestion and under his supervision that the problem was worked 

 out. During the process of the work collections of dodders in various 

 herbaria have been studied. The collection at the Missouri Botanical 

 Garden was opened to the writer and was of great value inasmuch as it 

 contains Engelmann's herbarium, including his types, and allowed com- 

 parisons nowhere else possible. Besides this the collections studied are 

 those of: University of Arizona, Boissier Herbarium, University of 

 California, Connecticut Experiment Station, private herbarium of Mr. 

 C. C. Deam, DePauw University, Gray Herbarium, University of Illinois, 

 Michigan Agricultural College, New York Botanical Garden, United 

 States National Museum, Wabash College, Rocky Mountain Herbarium 

 in the University of Wyoming, and Yale University. At the Gray Her- 

 barium and at the New York Botanical Garden, because of the limited 

 amount of time at the writer's disposal, it was impossible to list all of the 

 exsiccatae seen, though all specimens of Cuscuta were examined. The 

 writer was granted the privilege of borrowing a large number of specimens 

 from the latter herbarium, however, for more detailed study. To the 

 gentlemen in charge of all these collections I tender my sincere thanks 

 and appreciation of their courtesy in allowing me the privilege of studying 

 these materials, without which the work could not have been done ade- 

 quately. I also wish to thank Mr. F. H. Hillman of the United States 

 Department of Agriculture for the abundant specimens and samples of 

 seeds which he generously provided. Thanks are also due Professor 

 W. Dudgeon of Allahabad, India, for four photographs showing tree- 

 infesting dodders; as well as to numerous friends who have kindly sent me 

 specimens. 



HISTORY 



Choisy was the first, in 1841, to treat Cuscuta monographically. 

 Previous to this time little attention had been given the group. A few 

 new species had been described from time to time from different parts of 

 the world by travelers such as Humboldt and Gay. Choisy's paper, well 

 illustrated, included all the species then known, forty-one, a large number 

 being newly described by him. He considered the group as a genus 

 belonging with the Convolvulaceae and used characters of the stigmas to 

 divide it into two sections. The first section included those species 

 possessing acute or clavate stigmas and the second those with globose- 

 capitate stigmas. The second section in turn was divided into two sub- 

 sections on the basis of the inclusion or exsertion of the styles, a character 

 which is now considered of doubtful value inasmuch as the styles show 

 different lengths depending upon the stage of development. 



