E. R. Saunders 331 



If the above account is correct, then so far as can be seen a similar 

 result will ensue in the succeeding self-bred generations F-^, F^, &c., 

 since in each case the singles produced by self-pollination would appear 

 to result from the meeting of XYW ovules and xyw pollen. The record 

 obtained in F-^, so far as it goes, is entirely confirmatory. 54 families 

 were raised and all included some doubles, a result which may be taken 

 to establish the double-carrying character of all the F^ pollen grains 

 from which the F„ parents were descended. The totals obtained in the 

 whole number of F^ families were 354 singles and 372 doubles. Only 

 a few plants in each family were flowered ; they proved to be again all 

 singles with white plastids and doubles with creain plastids, thus 

 confirming the results obtained in F... 



We are thus led to conclude in regard to unions of the form 

 d-non-cream $ x cZ-cream ^ : {\) That segregation in the male cells 

 of the cross-breds exhibits the same peculiarity as in a sulphur-white, 

 and that the pollen grains do not carry XYW, although all these three 

 factors are present in the F^ zygote. Thus the pollen of F^ is similar 

 to the pollen of the (/" parent which was used to produce it. (2) That 

 the factor for whiteness {W) which is brought into the pedigree by the 

 % parent in combination with X and Y remains in association with 

 X and Fin the % gametes of F^. If exceptions occur in either case 

 they must be extremely rare. 



Mating 4. cZ-glabrous cream % x c^-glabrous and d-hosity non- 

 cream jf. 



The matiugs were the converse of those just described, d-cve&m 

 being here used as the % parent, rf-red as the ^. 



Three different crosses of this kind were made, three cream plants 

 being used as male (see p. 332). 



It will be convenient to consider the results under (a) and (6) 

 separately, since it may be that the appearance of an F„ single with 

 cream plastids in {h) — a combination not recorded in (a) — is due to the 

 impure nature of the cream plant used as the pollen parent in the 

 {b) mating. 



In matings of this type all single F^ plants will presumably be 

 derived from the union of XYvj ovules with xyW pollen, so that in 

 this case only X and Y are introduced by the female parent, W being 

 brought in by the pollen. We may therefore assume that here W will 

 be carried by at least some of the F^ pollen, though whether by all, and 

 if not by all, by what proportion, we cannot on purely a pr-iori grounds 



