rUE RECIPROCAL INFLUENCES OF STOCK AND CION 567 



both in nursery and in orchard, because of the earher ripening of the wood. 

 Prunus lusitanica is said to ripen its wood earher on Prunus Padus stock 

 than on its own roots and to withstand cold weather better, probably 

 on that account.^"* Budd^^ reports the Jonathan apple ripening its 

 terminal shoots better on Gros Pomniier "than on its own roots" and 

 states that "the hardiness of a variety is increased by the influence of a 

 stock with a determinate habit of growth. ... In our own State 

 [Iowa] we have evidence that by the selection of proper stock we can 

 grow Jonathan or Dominie on low, wet soils where they would not reach 

 bearing size, root-grafted . . . the main utility with us of top-working 

 on such prepotent stocks as Gros Pomier, Duchess, Wealthy, Wolf River, 

 etc., is in the way of fitting the less hardy scion for enduring the tempera- 

 ture of our test winters." 



Experience with grafted grapes in regions where winter killing is 

 important was more extensive in an earlier generation than in the present. 

 The literature of the times shows a tendency to agreement in the increased 

 hardiness of certain varieties such as lona and Adirondac on hardy stocks 

 such as Concord. Precise observations as to the reason for this were 

 not common, but the suggestion was made that lona roots were tender."^ 

 The increased hardiness was secured, if this be true, by the substitution 

 of a hardy variety in a tender part and not by changing the nature of the 

 cion. Here again, roots inducing early maturity appear to increase 

 hardiness. Nicholas Longworth,^^ after extensive trials, reported, 

 "Foreign vines grafted on our natives are equally tender as on their own 

 stock and are, with me, often killed down to the native stock." 



It is not, it should be noted, invariably the stocks inducing early 

 maturity that are hardiest. St. George stocks, as reported by Hedrick, 

 induced late growing in many cases; however, they suffered rather less 

 from winter killing than the other stocks tested. Hedrick suggested that 

 the deep rooting habit of this variety may be connected with its hardiness. 



Onderdonk^i^ and Vosbury^*^ reported that in the Gulf States the 

 trifoliate orange increased the hardiness of the varieties worked upon it 

 and attributed the hardiness to the deciduous habit of the trifoliate, 

 inducing a degree of dormancy in the cion varieties and thereby making 

 them more cold resistant. In the freeze of 1913 in Cahfornia lemons 

 worked on orange trunks proved more hardy than those on their own 

 trunks, hardier not only in the orange trunks but in the lemon tops. It 

 was suggested ^^^ that in some way the trunks of the trees modified the dor- 

 mancy of the tops. This condition was more apparent in young trees 

 than in those of bearing age. As in the Gulf States, trees on trifoliate 

 were somewhat hardier than those on other stocks. In cases of severe 

 injury, however, when the entire top has been killed, the trifohate 

 is unable to send up any sprouts and dies, though it has not itself suffered 

 any direct injury from the cold weather. 



