20 



The Journal of Heredity 



i'>i(i. 



Blush, alone, or in combination as the 

 Lemon Blush. The pink color seems to 

 be developed by the sunlight and is 

 most evident upon the sun-exposed 

 parts of the fruit. Such strains of 

 fruit are not mistaken for those with 

 solid pink flesh, and rarely show the 

 pink color far below the surface. Simi- 

 lar modifications are met with in the 

 lemon group, and here perhaps are due 

 to the clear skin, the color therefore 

 being actually deeper and the contrasts 

 with the shaded parts of the fruit more 

 I^ronounced, giving an appearance sug- 

 gesting the cheek of a peach. The 

 pink group shows differences in the 

 amount of the flesh color that are more 

 or less varietal. 



The skin of the tomato plays such an 

 important role in determining the color 

 of the fruit that it deserves considera- 

 tion here. Microscopically the skin 

 consists of the epidennal layer and 

 three or four layers of coUenchyma 

 cells, much smaller than those of the 

 underlying tissue and separating from it 

 more or less readily as the housewife 

 appreciates. 



Dr. Groth,' who has made an exhaus- 

 tive study of tomato skins, states that 

 "In the colored skins the yellow color 

 resides only in the cuticle and cuticular 

 thickenings . . . However, the skin 

 from any red tomato is at once dis- 

 tinguishable from that of any yellow 

 tomato under the microscope, because 

 the very crystals which lend color to 

 the interior of the fruit also occur in the 

 epidcnnis and other skin layers. For 

 this reason the skin of red tomatoes 

 always looks a shade darker when 

 scraped and spread on a white back 

 ground, than that of the corresponding 

 yellow forms." 



THUKN'i:SS .VXD II Al RIN'KSS 



Dr. Ciroth foiuid that there is a wide 

 range in the thickness of the skin among 

 the several types, and it is evident that 

 this may account for the many differ- 

 ences in the intensity of the fruit-color, 

 ])articularly in the kinds with orange 

 skin, and leads to slight variations when 

 kinds of the same color are bred together. 



R. H. A. Groth. Structure of Tomato Skins, Bull. N. J. Experiment Stalion, No. 228, Feb., 



lemon flesh and an eciual nvunber of 

 orange-fruited plants with the factor for 

 colorless skin unexpressed. 



One can only wonder how great 

 becomes the mixing in a field of plants 

 that results after three or more years of 

 breeding together of a red-fruited and a 

 lemon-fruited jjlant. The segregation 

 into the pure type should be done in the 

 second generation. 



The only remaining original type of 

 tomato fruit color to be here considered 

 is the so-called red, and this is the one 

 that embraces the majority of the 

 standard commercial sorts. In breed- 

 ing, the behavior of this group has been 

 considered in good measure in the 

 scheme that has just been given for the 

 pink-fmited kinds. For example, with 

 the lemon type the Fi will l)ring no 

 change, but in F2 the two pairs of factors 

 have full play, and there results the same 

 set of combinations displayed in Table I. 



When the red-fruited plants are bred 

 with the orange-fruited plants there is 

 the absence of the colorless skin, and the 

 only combinations are those of pink 

 flesh with lemon flesh, the skin being 

 orange in both parents and therefore 

 result in a quarter of pure P. O. (red) 

 and half P. 0. 1. (red) and the remain- 

 ing one-fourth P. 1. (pink). The half 

 will continue to yield pure and also 

 im])ure red-frtiitcd plants and the ])ure 

 pink strain. 



When the red and pink grou]3s are 

 bred together the flesh is the common 

 character, and therefore the results will 

 conform to that of a monohybrid. as 

 described above for the case when the 

 flesh gave the differing character. 



MODIFICATIOXS MiK FOfND 



As before remarked, this scheme f)f 

 allekmi()r])hs covers the case of fruit 

 colors in only a general way, because 

 there are seeming exce])tions. The 

 colors doubtless are subject to modifica- 

 tions that are likely due to environ- 

 mental factors. For example, the lemon 

 flesh is not constantly the same tint of 

 pale yellow; in fact there may be much 

 j)ink mixed with it, so that some com- 

 mercial varieties bear the name of 



