Sinnott and Durham: Summer Squash 



i8i 



solid white in color and green stripes 

 have appeared in yellow lines. Striped 

 plants have always bred true to striping 

 after it has appeared, thus indicating 

 that it behaves as a recessive character. 

 Green striped plants have appeared in 

 yellow striped lines, but never yellow 

 striped plants in green striped lines, 

 thus suggesting that the relation of 

 yellow to green in stripe color is similar 

 to that which holds between them in 

 the body color of the fruit. Indeed, the 

 stripe seems merely to be a region in 

 the fruit where the dominant body 

 color is inhibited in its expression and 

 where the recessive color is thus able to 

 manifest itself. The color of the stripe 

 will therefore depend on the genetic 

 constitution of the plant. In the case of 

 a white fruit, the stripe will be yellow if 

 the fruit has hypostatic yellow in its 

 genotype, but if this is absent the stripe 

 will be green. That this conclusion is 

 correct is indicated by the fact that 

 lines with white fruits showing green 

 stripes have been proved, through 

 breeding analysis, to contain no yellow. 



In a number of cases in yellow and 

 green fruits, stripes of the same color 

 as the body but deeper in shade occur 

 in the furrows. We are probably con- 

 cerned herewith an effect of the striping 

 factor on those factors which modify 

 the intensity of the body color. 



Striping was involved in four crosses, 

 the results of which are given in Table 

 II. 



In pedigree 21, where green striped 

 was crossed with plain white, striping 

 clearly behaves as a recessive and seems 

 to be due to a single factor difference. 



In the other cases, where white with 

 yellow stripes is crossed with plain 

 yellow, difficulties arise. The absence 

 of striping, brought in by the yellow, is 

 clearly not dominant, for the Fi in 

 every case shows stripes. In the F2, 

 however, there are a considerable 

 number of unstriped whites and most 

 of the yellows are unstriped. It should 

 be noted that in pedigrees 5 and 7, 

 where we have shown that there are 

 probably two independent factors for 

 white, the yellow stripes (perhaps 

 because of the excess of white) are pale 

 and in some cases are barely distin- 

 guishable; so that possibly some of the 

 plants recorded as plain wliite may 

 actually possess very faint stripes. 

 It is also possible that the factor for 

 plain color brought in by the yellow is 

 recessive to striping. The majority of 

 extracted yellows, however, are not 

 striped, and the further possibility 

 suggests itself that there may be linkage 

 between the factor for white and the 

 factor for striping. 



It is evident that plain white is domi- 

 nant over striping, with a single factor 

 difference involved. The relation be- 

 tween striping and plain yellow, how- 

 ever, is not entirely clear. 



SURFACE OF FRUIT 



In certain of the lines, the fruit sur- 

 face is entirely smooth; in others it is 

 very warty (Figs. 17 and 18); and in 

 still others it shows only a few warts, 

 scattered here and there (Fig. 17). 

 Smooth fruited plants have always 

 bred true, but warty ones have some- 



Table II. Inheritance of Striping in Fruit 



