104 LOCK : PRESENT STATE OF 



Further cross-breeding among the offspring of these crosses 

 has given rise to the following results : — 



Purple F 1 plants from the cross red X white when crossed 

 again with a pure purple strain yielded 34 plants all purple 

 (6 crosses). 



Crossed with different pure white strains they gave 44 

 purple plants and 26 white (15 crosses. Expectation equality 

 — not a very good ajiproximation to the expected result). 



Crossed with the pure red strain they gave 21 purple and 

 17 red (7 crosses. Expectation eqwdity). 



Among 16 red F2 plants examined (by self-fertilization) 10 

 yielded a mixed progeny of reds and white — 113 : 50 {Expec- 

 tation 3; 1), and 6 yielded red offspring only — 83 in 

 number. 



White plants of the same generation (F 2 from self-fertilized 

 F 1) were also examined by crossing with the pure red strain. 

 Some of these crosses yielded purple plants only, others purples 

 and reds, and others gCgam reds only.* 



Purple plants of the same generation when crossed with 

 pure {i.e., parental) whites yielded in some cases purple 

 plants only. In 5 cases they yielded a mixture of purples 

 and whites ISf purple : 19 white. 



(v.) The dark hylum was only observed in plants one of 

 whose parents at least showed the same character. Dark 



Red-flowered plants arising in a similar manner by the loss of the 

 factor P could also be preserved by selection, but they are compara- 

 tively vmcommon, and have not apparently been observed to give rise 

 to wliite as a further mutation. 



There is no reason for supposing that the loss of both factors is likely 

 to take place simultaneously — rather the reverse. 



But innvunerable white varieties exist, and it might besvipposed that 

 the loss of the factor P would have taken place in some of them. Such 

 aplant, however, could not be recognized, except by the test of crossing- 

 It would therefore not be selected, and its chance of survival would bo 

 small. Therefore, although many varieties still remain to be examined 

 from this point of view, it is qviite possible that the pure recessive white 

 will not be discovered among naturally existing varieties. It can, 

 however, readily be obtained by crossing. 



* So that white plants can be extracted which do not contain the P 

 factor : c/. prexdous note. 



t Cf. the somewhat wide deviation from equality shown by the 

 corresponding cross in the previous generation. 



