356 University of California Publications !?i Agricultural Sciences [Vol. 2 



agricultural plants the chromosome numbers are fairly low — 7 and 8 

 haploid, according to which 7 and 8 linkage groups are to be expected. 

 A genetic and cytological investigation in Trifolmm was started 

 by the writer at the Division of Genetics of the Department of Agri- 

 culture, University of California, Berkeley, in July, 1926, and carried 

 on until December, 1927. In this paper will be included only the 

 results of the cytological investigations and the attempts at species 

 crossing. I take great pleasure in thanking Professor E. B. Babcock 

 for laboratory facilities and give my best thanks to all the members 

 of the staff in the Division of Genetics for help and advice. I am 

 greatly indebted to Professor P. B. Kennedy and Mrs. A. Frederick, 

 of the Division of Agronomy, for the material and for help in 

 identification of the species used. Acknowledgment is also given to 

 the International Education Board for the fellowship granted to me. 



• MATERIAL AND METHODS 



Most of the material was grown from seeds furnished by Professor 

 Kennedy. The seeds of the American species had been obtained either 

 from plants growing wild or from plants grown one generation in the 

 greenhouse. Plants of these species have been compared with the 

 specimens in the Herbarium of the University of California and in 

 the collection of Professor Kennedy. In the nomenclature and group- 

 ing of these species I have followed McDermott (1910). The other 

 species used were for the most part well-known cultivated species, 

 with the exception of Trifolium glomeratum from Syzran, Russia, and 

 T. suhterranum, which was grown only to a seedling stage. These 

 seeds had been obtained from the United States Department of 

 Agriculture. The two strains of T. repens used were obtained from 

 the following sources: (1) T. repens var. sylvesirc, wild white clover, 

 plants growing wild on the campus of the University of California ; 

 (2) T. repens var. giganteum, Ladino clover; Italian white clover; 

 seeds from Vilmorin, France. Three strains of T. pratense, Italian, 

 Late Swedish, and Canadian, Avere obtained from the Central Experi- 

 ment Station, Ottawa, Canada. 



The chromosomes were studied in somatic divisions in root tips; 

 in two species the reduction division in the pollen mother cells was 

 also investigated. For the root tips the fixative of S. G. Nawaschin 

 (Karpechenko, 1927, p. 367) was always used. Buds for the study 

 of pollen mother cells were fixed either in Flemming's medium or 



