SECRETARY'S PORTFOLIO. 543 



and so leads to a movement of sap from the root upward or from one part of 

 the trunk to another. The flow of maple sap in spring illustrates this nicely. 

 During a cold night the air in the trunk contracts, and the space it occupied 

 is filled with sap from below ground. When the sun strikes the tree the 

 next morning, and warms it up, the bubbles of the gas again expand, and 

 drive the sap out wherever a twig has been broken or a hole bored into the 

 trunk. . 



Value of Leaves. — J. J. Thomas, in speaking of the value of leaves, says: 



A distinct illustration was presented to me many years ago, in the loss of all 

 the leaves of a plum-tree near midsummer, by what was termed leaf blight. 

 The plum was a small and very sweef variety, known as the small Yel- 

 low Gage. When the leaves dropped, the plums were about two-thirds 

 grown, and they had not acquired any of their sweet flavor, the taste being 

 bitter and immature. The heavy crop of small specimens was conspicuous on 

 the bare branches, and the fruit remained stationary in size and unchanged in 

 quality for about three weeks, when a new crop of leaves came out. The young 

 green plums then resumed growth, gained their naturally rich, golden color, 

 and their sweet and honeyed flavor. 



' A less striking instance recently occurred on a bush of the Missouri currant, 

 which was entirely divested of its foliage by the span currant-worm before the 

 currants were half grown. In a few weeks the abundant rains caused a new 

 growth of leaves, and the bush is now fully clothed, with the result that the 

 fruit has reached full size and perfect maturity. 



A less pleasing instance occurred in a thrifty vineyard of several acres, which 

 had just come into fair bearing. The owner, pleased with his success, resolved 

 to have an uncommonly fine crop by removing the leaves so as to let in the sun 

 on the growing and ripening grapes. He accordingly cut off all that portion 

 of the shoots immediately above the bushes. The grapes, thus deprived of 

 the food which the leaves had furnished, ceased growing. They were small in 

 size and destitute of flavor. But the loss of the crop was not all. The check 

 given to the vines nearly ruined the vineyard, and it was subsequently neglected, 

 aud came to nothing. 



Such facts as these show the importance of caution in summer pruning of 

 any kind, or in cutting back the shoots of newly transplanted trees after the 

 buds have opened. On one occasion, on a row of young apple-trees which had 

 been removed and reset, the needed cutting back had been delayed till the 

 leaves had partly opened. The delayed pruning gave so great a check that 

 none of the trees made a new growth more than an inch long. Others, which 

 had been timely cut back, grew from six inches to a foot. Of the different 

 kinds of trees, cherries suffered most from untimely pruning, and peach trees 

 least. The latter have more power to reproduce shoots and leaves. Cherry 

 trees have been killed by pruning out of season. 



Examples of this character often occur to attentive observers. In one case a 

 young hedge of the honey locust was nearly destroyed by shearing it closely 

 after growth had commenced. The Osage orange is less injured by this treat- 

 ment, as it has more power to reproduce growth. Xot being so seriously re- 

 tarded by summer pruning, hedges which have made full growth may be advan- 

 tageously held in check by cutting back in summer. 



The Rural Canadian makes the following comment in the same line of 

 thought : 



