142 Muhlenbergia, Volume 6 



A NEW STUDY OF CARDUUS 

 Bv George E. Osterhout 



In the Rocky mountains Cardmis is a large and difficult 

 genus. It is well represented from the plains to the alpine re- 

 gions. Iri his Flora of Colorado Dr. Rydberg lists thirty-two 

 species, while the the Illustrated Flora of Britton and Brown 

 lists only sixteen species for the northeastern United States and 

 Canada. Anything like a full list of the forms found in Colo- 

 rado has never been made, and forms resembling some of the 

 known species in some characters, but differing in others, have 

 made the study difficult and discouraging. This is especially 

 true of the mountain species. Several forms have been collected 

 which in a general way have a strong resemblance to C. Anicr- 

 icanus (Gray) Greene, and yet are far from being .ypical. In 

 the higher mountains forms resembling C. Parryi (Gra) ) Greene, 

 and C. scopulorum Greene, have been collected. These forms 

 were puzzling I student, for it did not seem possible to 



make .is many species as there are forms, and it did not seem to 

 be a satisfactory disposition of them to place them with species 

 which were regarded as typical. 



The first real helpful solution of this difficult problem was 

 suggested by Dr. Rydberg in the Bulletin of the Torrey Botan- 

 ical Club for November, 1910. He regards these perplexing 

 forms as hybrids, and lists fourteen as occurring in Colorado, 

 with five others in contiguous territory. In this list C. amcri- 

 canus is one of the supposed parents of four forms, C. acaules- 

 cem of three, and C. griseus of three. Various other species 

 make up Ihe other supposed parents ami the other hybrids. 



It may be that some of the forms which Dr. Rydberg con- 

 siders hybrids will prove to be independent species, and there 

 may be other hybrids as yet unnoticed. However, Dr. Rydberg 

 has begun a new line of study which ought to induce more care- 

 fttl observation, and hung a better collection of Carduui. These 

 plants have not been attractive to collectors, probably because 

 they are disagreeable to handle, and arc cumbrous specimens. 

 There is need of much more collecting and study before the 

 genus can be satisfactorily worked out for the Colorado flora. 



\'u Windsor, < '■ ilorado. 



