Mar. II, 1918 Sterility in the Strawberry 627 



produced a number of seedlings which were as sterile as the parent. 

 (All the progeny have not yet flowered.) 



Sufficient pistillate varieties have not been studied to indicate defi- 

 nitely whether there is always a distinct difference between the ability 

 of these and of the hermaphrodites to set fruit on the later flowers; 

 however, a comparison of the percentage of fruit set on the tertiary 

 and quarternary flowers of the pistillate and staminate varieties reported 

 in Tables III and IV would seem to indicate that the former are de- 

 cidedly more fertile than the latter, as is also the case in the wild forms. 

 Darrow (9) reports that Mr. Hubach will use only pistillate varieties 

 as the fem.ale parents because of the decrease in fruit production when 

 hermaphrodites are used as both parents. 



A cytological comparison of the sterile pistils of wild males and the 

 sterile pistils of hermaphrodites may give further evidence as to the 

 origin of sterility in the varieties which produce many nubbins and 

 entirely sterile flowers. Strasburger (jp) has shown that in a male 

 resulting from a cross between F. mrginiana 9 and F. elatior 3- , the 

 pistils which are apparently ready for fertilization already, in longi- 

 section, show a mass of degenerating material which contains the embryo 

 sac mother cell. This may or may not be the condition in the pure 

 forms of these species and in the sterile pistils of cultivated varieties. 



To the commercial grower of strawberries as well as to the breeder 

 the question of variation of fertility under varying conditions of environ- 

 ment or culture is of importance. Evidence which indicates that fer- 

 tility is affected somewhat by environmental or seasonal conditions is 

 given by the seedling which in the spring produced strictly male flowers 

 but which in the summer and early autumn produced fertile pistils as 

 well as stamens. Further, it is a matter of common observation that a 

 bed of berries, if allowed to fruit more than one year, will produce an 

 increasing number of small berries and nubbins. Of actual observational 

 evidence the following indicates that growth conditions have something 

 to do with sterility: A variety, named "Glenville" for convenience, was 

 sent to the Station with inquiries as to why it did not set fruit. Plants 

 of it were grown in the greenhouse during the late winter, and, although 

 they produced numerous fruiting stalks ancl an average of 13 flowers 

 per stalk, only an occasional primary or secondary flower set fruit. 

 Some of these plants, after having been grown in benches, were put 

 into pots and given little attention. On June 5 they were fruiting, 

 and a count was made of the flowers which had set. On 6 fruiting 

 stalks there was a total of 43 flowers, an average of slightly over 7 per 

 stalk. Of these, 22 set fruit. Of 6 primaries there was i which set, of 

 12 secondaries 10, of 19 tertiaries 11, and of 6 quaternaries none set. 

 The previous 3'car some plants of this variety had been planted in the 

 field ; and 20 days after taking the above notes, observations were made 

 on the field plants. Of 105 fruiting stalks examined, bearing a total of 

 1,292 flowers, an average of 12.3 flowers per stalk, there was a total of 



