{a)< 



332 Dovhleness in Stools 



predict. Similarly we may suppose that some of the F^ ovules which 

 carry XY will lack W, though whether all will prove to be thus 

 deficient we also cannot foretell. 



MATING 4. Summary of results. 



Parental Types 

 d-glabrous cream (Plant H) i x d-glabrous red J 



„ „ (Plant G) ? X d-glabrous red <f 



„ „ (Plant G) ? X d-glabrous white i 



Totals in the case of the immediate sowings — 49 66 48 — 65 



delayed sowingsi — 193 320 137 — 263 



,,, ( ? d-glabrous cieam 9 d-hoary white <f 2 9 19 10 1 16 



^ ' ] (descendant of Plant A') (intermediate strain)- (after 3 years) 



The experimental result was an F2 of 49 s. and 66 d. in the case of 

 the immediate sowings, and 193 s. and 320 d. in those that were delayed 

 until the second or third year after harvesting. 513 plants were 

 flowered and all had white plastids. Singles and doubles with cream 

 plastids either do not occur, or if they are formed they must be present 

 in very small numbers. We may therefore conclude that all (or all but 

 very few) of the F^ pollen grains must carry whiteness as well as double- 

 ness. Thus both here and in the reciprocal type of cross, so far as 

 experiment has yet gone, we find that the F^ pollen appears to carry 

 chiefly if not exclusively the particular combination of factors which is 

 present in the pollen of the father. Although the Fi zygote is hetero- 

 zygous in regard to these factors, the allelomorphs brought in by the 

 mother appear to be absent (or if not wanting altogether then very 

 rare) in the male cells of the cross-bred. But if all (or almost all) the 

 Fi pollen is carrying W it is evident that the distribution of W among 



' See Appendix, note 1, p. 361. - See note p. 326. 



