THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN. 



Vol. IX, No. 5.] DECEMBER, 1914. RJffiKSI's 



A Comparative Anatomical Study of Some 

 Species of Xanthium. 



BY NORA E. DALBEY. 

 Plates XVI to XXII. 



INTRODUCTION. 



EIGHT species of Xanthium are now recognized in the terri- 

 tory east of the one hundredth meridian. One species, 

 which in the first edition of the Illustrated Flora of the United 

 States and Canada, by Britton and Brown, was called Xan- 

 thium canadense, is now known to be two distinct species, Xan- 

 thium americanum Walter, and Xanthium pennsylvanicum 

 Wallroth 



In 1912 Prof. Charles A. Shull, of the University of Kansas, 

 for the purpose of securing pure lines for experimental work, 

 made a collection of the seeds of the three main types of Xan- 

 thium found in the fields about Lawrence. Of the three types, 

 one resembled closely Xanthium pennsylvanicum, another 

 agreed well with the description of Xanthium americanum, and 

 the third was a form distinguished by short globose burs, to 

 which he gave the provisional name of Xanthium globosum. 

 He thinks this type is new, as it has never been described 

 among the published species of Xanthium. Professor Shull 

 selected seeds from one plant of each type, and planted them 

 in pots in the laboratory, and about the first of June trans- 

 ferred them to the breeding grounds. It was expected that the 

 plants would show the characteristics of hybrids, but instead, 

 they developed with uniformity, showing three distinct types, 



(57) 



2 — Univ. Sci. Bull., Vol. IX, No. 5. 



