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56 EXPERIMENTS IN BLUEBERRY CULTURE. 



The withering of the tip inchides the uppermost leaf rudiment and 

 the growing point of the stem inclosed within its folded base. The 

 tissues turn brown and become dry, and the growth of that axis is 

 terminated. The resumption of growth from such a stem, if it 

 occurs, takes place through the formation and expansion of a bud in 

 the axil of the leaf next below the withered one. This withering of 

 the tip is readily distinguishable by its color from a partial blacken- 

 ing of the uppermost tender leaves which sometimes occurs, appar- 

 ently a pathological disturbance of a temporary character and usually 

 not affecting the growing point of the stem itself. The brown wither- 

 ing of the tip seldom takes place when the leaf rudiment involved in 

 the withering is more than 0.1 inch (2.5 nnn.) in length. ^Yhen longer 

 than that it usually keeps on expanding. This withering of the tips 

 has been almost wholly prevented when the shock of transplanting 

 was rendered as light as possible by suitable precautions, including 

 (a) a soil in perfect condition for the nutrition of the plants, espe- 

 cially that in wliich the peat is well rotted (p. 61) ; {h) the transfer 

 of the plants to their new bed without injury, especially without 

 destroying any part of the roots; (c) the shading of the plants 

 from direct sunlight for tAvo weeks or more, until their new root 

 growth is well established, and their subsequent gradual adjustment 

 to full sunlight; and [d) the holding of the transplanted plants in 

 a warmer, moister atmosphere, about 65° at night and 80" F. in 

 the daytime. ^A^iether or not this last condition had a real influence 

 on the prevention of the tip withering is not definitely known. 



The stagnation of the uppermost leaf rudiment does not attract the 

 inexperienced observer's attention so readily as its withering. With 

 a little experience, however, it is easily detected. Ordinarily the 

 leaves of a growing stem follow each other at a rather close interval, 

 so that by the time a half-grown leaf is ready to flatten out, from its 

 boat-shaped folding in the younger stage, the succeeding leaf is com- 

 monly a third or more the length of the one that is flattening (fig. 

 22). A^Hien stagnation occurs, however, the uppermost leaf rudiment 

 promptly stops growing, usually at a length of 0.04^ inch (1 mm.) or 

 less, while the young leaf next below it goes on flattening and grow- 

 ing to nearly its normal size. The end of the stem, therefore, shows a 

 nearly full-grown flat leaf with a minute leaf rudiment at its base 

 seldom more than a fifth and often not more than a tenth its own 

 length. 



The purpling of leaves, to which allusion has been made, does not 

 refer to the reddish translucent appearance of the growing twig tips. 

 That is the normal coloration in the blueberry, as it is, for example, 

 in the rose. The purpling now under consideration occurs in the 

 mature leaves, which are normally green, and is of a dark shade. It 

 is commonly accompanied by a conspicuous reddening of the leaf 



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