14 PRINCIPLES AXD PRACTICE OF PRUNING 



occurs. It may be said, parenthetically, that this bleeding 

 may produce ill effects instanced as follows : 



15. Vine bleeding. C. C. Newman has demonstrated 

 the evil effect of late spring pruning of muscadine grape- 

 vines.* 



Two vines growing side by side were pruned, one November 15 

 and the other February 15. The vine pruned in November did not 

 bleed at all as the spring advanced and produced a wonderful crop 

 of fine fruit. The vine pruned in February began to bleed as soon 

 as the weather turned warm, slowly at first, but bleeding more 

 freely as the spring advanced. Drops of sap could be seen steadily 

 dripping from the end of each vine that had been cut. The vine 

 pruned in February was 10 days later in putting out leaves than the 

 one pruned in November. The growth was very feeble and it set 

 very little fruit, most of the canes dying during the summer. 



To form some idea as to the amount of sap that would flow from 

 a vine that had been pruned too late in the season, a third vine was 

 pruned in November, and on March 20 one cane, 1 A inch in di- 

 ameter, was cut on the same vine and a rubber tube fastened over 

 it so as to conduct the sap to a large glass jug, the mouth of which 

 was closed with a cork, through which the rubber tube passed. The 

 vine began to bleed freely from the cane cut March 20, but the canes 

 cut in November did not bleed at all. A careful record was kept 

 of the sap collected, and in four weeks from the time the cane began 

 to bleed, 23 pounds of sap had been collected from this one cane. 

 The loss of sap through this cane affected the entire vine, and its 

 growth was checked considerably. 



16. Transpiration is the passage into the air of water 

 in vapor form from leaves and other green and growing 

 parts of plants. Thus a very great part of the water ab- 

 sorbed by the root hairs finds its way into the air. Cer- 

 tain plants (eucalyptus trees), because of their ability to 

 transpire immense quantities of water, are used to re- 

 move excess water from soils that cannot readily be 

 drained in any other way. As instances among agricul- 

 tural plants it may be mentioned that experiments with a 

 little tree have shown that (proportionately) an apple tree 

 30 years old would probably transpire 250 pounds of 

 water a day, or about 20 tons during the growing season. 

 At this rate an apple orchard with trees set 40 x 40 feet - 



* S. C. Bulletin 132, Page 7. 



