316 MASSACHUSETTS AGRICULTURE. 



impeded in its descent, the parts above became larger, the fruits 

 swelled and ripened earlier. This corresponds with our own 

 experience. 



This process may be applied to other fruits, the effect of 

 detaining the sap unnaturally in the branches being to force the 

 plants to produce blossom buds instead of leaf or branch buds. 

 It was before known that any thing which checked the growth 

 of a fruit tree hastened the production of fruit ; it was, how- 

 ever, reserved for Mr. Knight to show the causes, and to submit 

 the whole process to rules as certain as are known in any other 

 branch of natural science. The late Mr. Lowell, of Roxbury, 

 tried this plan on twenty young pear trees, which had been 

 grafted from ten to twelve years without giving fruit. The 

 branches thus operated upon bore full fruit, while every other 

 branch was barren and unprolific. On some trees he girdled 

 one, and on others two to five branches. He found equal 

 success on plums. Mr. Knight, from whose theory the experi- 

 ments liave been derived, thinks it will shorten the longevity 

 of trees subjected to it. Mr. Lowell, on the contrary, did not 

 apprehend this. He thought that judicious girdling was nearly 

 the same with grafting; that produces a similar interruption 

 of the sap ; a callous is formed between the original stock and 

 the graft, and yet we see the branches continue productive and 

 enjoy excellent health. 



The Isabella vine suffers more or less every winter. Long 

 shoots of the previous year, and occasionally the whole vine, is 

 what is called winter-killed. Many attribute this to extreme 

 cold. We apprehend that it is invariably produced by the 

 warm days of that season. In this our variable climate at 

 night we have the thermometer at zero, followed the next day 

 by a bright sun with the warmth of spring. Any one may 

 satisfy himself of this who has two vines trained upon a wall or 

 building, exposed to the sun in winter. If he will but take 

 one of these down, and lay it along its whole length upon the 

 ground, he will ordinarily find the one left up through the 

 winter filled with dead wood, while that upon the ground is 

 uninjured. This does not apply to those grown upon an open 

 trellis, where the air circulates freely. Now if the sap of trees, 

 particularly the grape, is " always in motion, at all seasons, and 

 vinder all circumstances, except in the presence of intense cold," 



