No. 626] MENDELIAN BEHAVIOR 



237 



The green individuals Nos. 2, 3, 9, 13, 15, 16, 18, 19, 

 20, 25, 29, 30 were homozygous for greenness and gave 

 pure green progenies. A progeny of several thousand 

 plants was grown from each individual. 



Of 8,123 plants descending from heterozygous green 

 individuals analyzed in Table II, 2,004 or 24.6 per cent, 

 were white-stemmed recessives. It is evident that these 

 figures for the extracted recessives also approach very 

 closely the theoretical 25 per cent. Mendelian ratio which 

 obtains for contrasted characters in simple hybrids. 

 This ratio of 24.6 per cent, extracted recessives of the 

 aurea type descending from green heterozygous indi- 

 viduals, is very close to the ratio 24.3 per cent, obtained 

 in a count of 25,000 individuals descending from F^ 

 plants. Since 12 of the 28 green F- plants tested were 

 homozygous for greenness and gave all green progenies, 

 it is evident that these were extracted dominants. 



The progenies of 20 extracted white-stemmed aurea 

 recessives of the F^ generation were also studied. Sev- 

 eral thousand plants were growTi from each of the 20 

 individuals, and all proved homozygous for the aurea 

 charaetiM-, etc. 



liETiAvioK OF Back Crosses 



First generation plants of the original cross No. 35080 

 (white-stemmed aurea) ? X No. 1 from India (green- 

 stemmed Rust tea) S were now crossed with the parent 

 green-stemmed and white-stemmed aurea types. 



In the back cross with the recessive white-stemmed 

 aurea parent 591 plants were obtained of which 303 were 

 green-stemmed individuals, and 288 were aurea. These 

 figures approach the theoretical 1:1 ratio which may be 

 expected in such crosses. 



In the back cross with the dominant green-stemmed 

 type, 280 plants were obtained, all of which were green- 

 stemmed. 



From these results obtained with the cross between the 

 green-stemmed types of .V. rusi'iva and the distinctive 



