Killing of Plant Tissue by Low Temperature 273 



Average percentage started on trees making large growth (cut 



back) 20.5 



Average percentage started on trees making small growth (not 



cut back) 31.2 



Number of varieties in which trees not cut back started first. . .20 



Number of varieties in which trees cut back started first 3 



Number in which both started about equally 4 



Quoting from the publication referred to: 



"It will be seen that only two-thirds as large a percentage of 

 buds started on cut back trees as on trees not cut back. It would 

 be expected then that when ninety per cent of the buds had started 

 on trees making small growth, only sixty per cent of those on trees 

 making a large growth would be started. This is borne out in the 

 above table. If we take the average of buds started on twigs taken 

 December 22nd, or later; that is, when the resting period is nearly 

 ended, we have: 



"For trees making large growth (cut back) 28.3 per cent started; 

 for trees making smaller growth (not cut back) 48.6 per 

 cent started. 



"Taking only those varieties in which one tree had sixty per 

 cent of the buds started, and therefore may be considered to have 

 finished its resting period, we have as an average: 



"On trees making large growth (cut back) 44.3 per cent of the 



buds started; 

 "On trees making smaller growth (not cut back) 83.4 per cent of 



the buds started." 



Results during the previous season when the difference in vigor 

 of the trees was greater, were even more conclusive though perhaps 

 not enough buds were used in the experiment. Thus with Elberta 

 buds on twigs gathered December 2, 1905, 66 per cent of those from 

 slowly growing trees clearly showed swelling by December 21, while 

 none from the vigorously growing cut back trees showed any swelling. 

 I-^vcn when the buds from vigorous trees were counted as started, 

 ihey had not generally made as much growth as had those from weak 

 trees. It should be said, too, that the trees listed as weak trees 

 were of average vigor when compared with those of most commercial 

 orchards. 



Since the iniblicaLion of that bulletin this station lias nuule ob- 

 servations on the effects of severe pruning and late growth on the rest 

 period of buds in the extreme southern portion of Missouri wlure 

 there are many days in January and February warm enough to start 



