THE INHERITANCE OF FLOWER TYPES AND FERTILITY 
IN THE STRAWBERRY 1 
W. D. Valleau 
(Received for publication August 18, 1922) 
In a study of sterility in the strawberry begun by the writer in 1914, 
a portion of the work was directed toward determining the underlying 
factors causing “nubbins” or imperfectly developed berries. These are 
commonly produced from the tertiary and later flowers of the inflorescence 
of many cultivated varieties of strawberry and result in considerable loss 
of fruit toward the close of the picking season. 
A study of the fruiting habit of the wild American strawberries and of 
the cultivated varieties proves conclusively that the production of nubbins 
is directly related to pistil sterility, and that pistil sterility is decidedly more 
prevalent on plants with certain flower types than on others (7). Therefore, 
since the question of fruitfulness in the strawberry is primarily one of sex, 
a thorough knowledge of the flower types and of their inheritance is essential 
to the strawberry breeder if his work is to be other than blind crossing and 
selecting for chance high-yielding clones. 
The work on the inheritance of flower types in the strawberry has been 
discontinued by the writer, but, as some facts have been determined, he 
presents the data obtained and the conclusions drawn from them. 
Flower Types in the Strawberry 
In the cultivated strawberry, pistillate and perfect flowers are commonly 
encountered. The pistillate flowers bear small abortive stamens which 
have never been observed by the writer to produce pollen. The pistils are 
generally very fertile, producing perfect fruits from most of the flowers and 
comparatively few nubbins. The perfect-flowered varieties develop anthers 
which produce varying amounts of normal pollen. As a class, these varieties 
are less fertile than the pistillate varieties and produce a higher percentage 
of nubbins and of sterile or male flowers (7). 
The wild species of American strawberries may be divided into two 
types: those which bear only perfect flowers,' as Fragaria americana, and 
those which are dioecious. The pistils of the former species are very fertile, 
and nubbins or sterile flowers are seldom seen. The dioecious types produce 
pistillate plants and plants which apparently are hermaphrodites but are 
in fact staminates. The pistils of the pistillate clones are usually fertile, 
but the pistils of the staminate clones are rarely so, and the few berries 
1 Paper No. 338, Journal Series, University of Minnesota Agricultural Experiment 
Station. 
259 
