JOINAL OF AGRiaiLTIIAL RESEARCH 



Vol. XII Washington, D. C, March ii, 1918 No. 10 



STERILITY IN THE STRAWBERPvY ^ 



By W. D. Valleau 



Research Assistant in Fruit-Breeding Investigations, Agricultural Experiment Station 



of the University of Minnesota 



INTRODUCTION 



This paper is a report of studies on the sex condition in strawberries 

 (Fragaria spp.) which have been carried on during the past four years. 

 The study of pistil steriHty and anther abortion in the cultivated varieties 

 and wild species, which are the result of the strong tendency of this 

 genus toward dieciousness, has received considerable attention; but the 

 primary object of the investigation has been to find, if possible, some 

 satisfactory explanation for the phenomenon of pollen abortion, which 

 is so prevalent among heterozygous plants or plants of hybrid origin.^ 



MORPHOLOGY OF THE FLOWER PARTS 



INFLORESCENCE 



The inflorescence of our cultivated strawberry and of Fragaria vir- 

 giniana, which it closjely resembles, is a dichasial cyme or sometimes, 

 especially in certain cultivated varieties, a pleiochasium. The two 

 lateral branches of the relatively main axis are not always equal either 

 in size — that is, number of flowers borne — or in time of flowering. The 

 pedicel of the primary flower is generally inserted a short distance from 

 the joint of the two secondary branches and on the smaller of the two. 

 The primary flower of the largest lateral branch usually opens directly 

 after the primary flower and before that of the smaller lateral branch. 

 The arrangement of the flowers and order of blooming are shown in 

 figure I. 



Variations from these types are not uncommon. In some cases the 

 primary flower is lacking ; in others, the primary stalk seems to be made 



1 Published, with the approval of the Director, as Paper 94 of the Journal Series of the Minnesota Agri- 

 cultural Experiment Station. 



2 The work was begun at the suggestion of Dr. M. J. Dorsey, of the Minnesota Agricultural Experiment 

 Station , and I wish to express my thanks for the help and encouragement which he gave diuing the progress 

 of the work. I also wish to express my appreciation of the assistance given by Dr. C. E. Allen, of the 

 Department of Botany, University of Wisconsin, in a portion of the cytological studies and for space 

 kindly furnished me in his laboratory during a month in 1915. 



Journal of Agricultural Research. ' Vol. XII, No. 10 



Washington, D. C. Mar. 11, 1918 



mj Key No. Minn, aj 



(613) 



