Abscission of Flowers and Fruits of the Apple 



75 



a meter of conducting 

 tissue of the twig was 

 apparently sufficient to 

 reduce the pressure to 

 a point at which bud- 

 pushing could occur; 

 hence, the first vigor- 

 ous buds to open were 

 those nearest the tops 

 of the twigs. Weak 

 spurs apparently 

 offered greater resist- 

 ance to the passage of 

 water; hence, they 

 pushed first because 

 they were not over- 

 supplied with water. 



It has been shown 

 previously that vigor- 

 ous, heavy spurs are 

 usually provided with 

 conducting tissue of 

 comparatively large 

 diameter. This experi- 

 ment shows that the 

 large, plump buds 

 which produce the 

 heavy spurs are more 

 abundantly supplied 

 with water than the 

 smaller buds. 



The difference in leaf 

 area between the vig- 

 orous and the weak 

 spurs is probably due, 

 in part at least, to the 

 difference in water sup- 

 ply, or, m-ore accu- 

 rately, sap supply. 

 The vigorous spurs 

 have larger leaves 

 than the weak spurs 



— B 



H 



Fig. 5. 



APPARATUS FOR FORCING WATER INTO THE ENDS 



OF TWIGS 



The pressure is supplied by a column of water three meters long. 

 This column is maintained at approximately the same level by the 

 water in the funnel. A, which is connected to the tube, C, by the union 

 at B. The tube passes thru the cork, F. This cork is also provided 

 with holes for the twigs, D. The twigs are from three to four years 

 old and about one meter long. After these twigs and the tube have 

 been inserted, the bottle, G, is filled with water. The cork is then 

 flooded with warm paraffin. After this has become firm the pressure 

 is applied. Check twigs are placed in the bottle H 



189 



