APPENDIX. 203 



'ispell" of warm weather succeeds a cold and backward spring, varieties of 

 all these groups will come on nearly together and cross-pollination will re- 

 sult. In some places the blooming seasons of these groups overlap so that 

 some varieties of each might be used regularly for cross-pollination. 



THE MUTUAL AFFINITY OF VARIETIES. 



Another point to be looked after when selecting a jwllenizer for Kieffer. 

 or for any other self-sterile variety, is the mutual affinity of the two. That 

 is, will the pollen of the pollenizer fertilize the pistils of the self-sterile va- 

 riety readily and also develop them into high-grade fruit V At present but 

 little is known about this matter. Taking first the possibility of cross-pol- 

 lination between varieties of different species, there seems to be no doubt 

 but that many varieties of native, Japanese, and domestic plums will fertilize 

 each other. Orchard experience in many places indicates this; as when 

 Satsuma is used to pollinate ( "oe Golden Drop in California prune orchards. 

 Several successful crosses between the three were also made at Ithaca the 

 past season. Among these are Abundance X Grand Duke (Fig. 84), George- 

 son X Way land, Berckmans X Goe Golden Drop, Coe Golden Drop X Sat- 

 suma. That is, if we wish to use Satsuma as a pollenizer for Coe (iolden 

 Drop, or Lombard for Wild (ioose, the probability is that the combination 

 would work, if the two varieties bloom together ; but since the three groups 

 usually bloom at somewhat different periods there can be no general cross- 

 pollination outside the limits of the species. 



Numerous crosses and common orchard practice have also shown that the 

 European pears, as Bartlett, and the Sand pear hybrids, as Kieffer, will fer- 

 tilize each other regularly when they bloom together. Several Kieffer 

 ruits from Bartlett pollen, and Bartlett fi-uits from Kieffer pollen, were se- 

 cured in the crossing work of 1899. In fact, my experience has been that if 

 Kieffer pollen is put on the pistils of our common pears, of the European 

 class, it wdll usually produce larger fruit than pollen from most varieties of 

 that type. Kieffer is a good pollenizer for Bartlett, Angouleme, Clapp, 

 Nellis, and like varieties, when they bloom together. In Fig. 81, compare 

 the size of the Seckels which received Kieffer pollen with those which had 

 Lawrence pollen. The specimens shown are typical of thirty fruits secured 

 from these two crosses in 189!». 



It is necessary to stndy not only the mutual affinity of varieties belonging 

 to different species, but also of varieties of the same species. Some varie- 

 ties will not fertilize each other, though blossoming at the same time. Kerr 

 has found that Whitaker plum will not fertilize Wild Goose, nor will Early 

 Red help Caddo Chief. Again, the pollen of some varieties will give better 

 fruit than that of others when used on the pistils of self-sterile or even on 

 self-fertile varieties. There is very little definite knowledge as to what va- 

 rieties are best adapted for pollinating self-sterile sorts. Waugh and Ken- 

 have studied this point with native plums for several years and their judg- 

 ment is united in a table of recommended pollenizers for plums (Twelfth 

 Report Vt. Ag. Ex. Sta. ). A few results from crosses made at Ithaca in 

 1899 will illustrate this point. Fig. 81 shows the comparative size of Seckel 



