THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN. 



Vol. X, No. 6.] January, 1917. [ Zl'xx%Tl 



An Anatomical Study of Cycloloma atripUcifolium. 



BY DUDLEY J. PRATT. 



A thesis submitted to the Department of Botany and the Faculty of the Graduate School in 

 partial fulfillment of the requirements for the master 's degree. 



INTRODUCTION. 



CYCLOLOMA ATRIPLICIFOLIUM is a coarse annual na- 

 tive to the central part of North America. The typical 

 form of this hardy xerophyte is found in the Niobrara sand hills, 

 according to the Phytogeography of Nebraska ('09). There the 

 small, slender, moderately branched form found in other locali- 

 ties becomes a great bushlike type (5 dm. to 2 meters in diameter 

 and 1 meter high), called the giant tumble weed, which is well 

 adapted to the tumbling habit because of its subglobose, compact 

 top and innumerable seeds. The spreading tops and close ag- 

 gregations of these tumbleweeds, sometimes several hectares in 

 extent, crowd out other plant growth from the sandy plains or 

 summits of the sand hills. On tilled soil, however, the smaller 

 form of this weed is not hard to combat. The Iowa Geological 

 Survey ('13) states the weed is easily exterminated in that state 

 by cultivation. 



There has been no anatomical work done on Cycloloma, recorded 

 in the literature accessible to the writer, but there has been some 

 ecological study of the genus, and of the species atriplicifolium. 

 Bentham and Hooker ('80), and Engler and Prantl ('89), classify 

 Cycloloma under the Chenopodiese, and describe the genus. Sole- 

 reder ('08) discusses the anatomical features of the Chenopodiese, 

 but does not include Cycloloma among the genera mentioned. De- 

 scriptions of both the genus and species are given by Britton and 

 Brown ('13), Coulter ('09), and Gray ('08). 



The plant studied was collected by Professor W. C. Stevens, 

 of the University of Kansas, September 5, 1915, on dry upland 



(87) 



