Mar. II, 1918 Sterility in the Strawberry 641 



pollen present in the bags while the later flowers were in condition for 

 pollination. 



In order to determine to what extent parthenogenesis or parthenocarpy 

 might possibly enter into the above results, bags were put over 67 clusters 

 of 22 pistillate varieties. Of a total of 661 flowers covered, 55 set some 

 achenes. Of these, 52 were found in 6 bags which had been accidentally 

 split, thus accounting for the probable pollination by insects. Of the 

 remaining three fruits, which developed in apparently tight bags, two bore 

 I achene each and the other 7. Significance can hardly be attributed 

 to the setting of these few achenes, since the chances for accidental 

 pollination, to this extent, are relatively great. It may therefore be 

 concluded that parthenogenesis does not exist in the cultivated strawberry. 



A condition which might possibly be attributed to parthenocarpy 

 occurred in the Buster variety, in which 9 flowers of the 22 bagged 

 showed a very decided development of the achenes with no accompany- 

 ing development of the receptacle. These achenes contained no embryos. 

 In the strict sense of the word parthenocarpy in the strawberry could 

 only be applied to a development of this kind. A more comprehensive 

 use of the term might include the development of the fleshy receptacle. 

 Ordinarily, flowers which set only one or a few achenes develop the 

 fleshy receptacle only at corresponding points, due probably to the 

 stimulus of fertilization. In perfect varieties receptacles are often 

 found in which development has taken place not only at the base of 

 the pistils but also about the base of the stamens. In 3 out of 10 

 bagged flowers of the pistillate Red Bird variety, the fleshy receptacle 

 developed about the base of the staminodia forming a red fleshy circle 

 about the dried pistils. Two flowers of Crescent, also an imperfect 

 variety, developed normal fleshy berries, one bearing one achene and 

 the other none. Apparently these receptacles developed without the 

 stimulus of fertilization in the same way as that at the base of the stami- 

 nodia in Red Bird. 



POLLEN DEVELOPMENT 



As Mendelian and, in fact, most genetic results are dependent upon 

 the segregation of determiners during the formation of gametes and to 

 their recombination again at the time of fertilization, any processes 

 which interfere with the normal procedure should be carefully studied 

 and, if possible, their nature determined. 



There are a number of ways in which the normal order may be dis- 

 turbed, at least there are various outward expressions of them. The 

 condition in the Phylloxera spp., as pointed out by Morgan, in which 

 half of the spermatids degenerate regularly, while the other half con- 

 tinue and form normal spermatozoa, and the relationship between 

 degeneration and the absence of the accessory chromosome is so well 

 known that it needs no comment. Gates (iS) has shown that in 



