331 



known, the extremely luxuriantly growing American vines consume much 

 greater amounts of water. 



Tissue warts of this kind are much more abundant than is generally 

 assumed and occur also on decorative plants\ They are reactions of the 

 plant body to a wound stimulus or internal disturbances of equilibrium in 

 the supply of water and nutritive substances. 



Watersprouts. 



By the term watersprouts, watershoots, or suckers, are understood ex- 

 ceedingly vigorous foliage shoots with long internodes, which grow up 

 perpendicularly from old branches or trunks. Often trunks covered with 

 lichens are distinguished by abundant sucker formation. Since the suckers 

 grow up into the crown of the tree, they produce wood, and, indeed, un- 

 fruitful wood, at the very places which it is desirable to keep free from 

 branches in order that sufficient light and air may reach the inner part of 

 <-he crown. It is not advisable, however, to remove the suckers, if the 

 cause of their formation is not removed at the same time. In many cases 

 the cause may be found in an impervious subsoil. The roots of the vigorous 

 tree reach this impenetrable layer sooner or later, which not infrequently is 

 y vein of closely cemented sand containing iron. The absorption of food 

 stufifs is limited by this, the tree forms only short shoots and smaller leaves, 

 but still bears fruit. In a warm and damp spring, when all trees make a 

 strong foliage growth, the energy of the weakened tree also appears to be 

 increased by the favorable vegetative conditions. The strong upward force 

 of the water causes the formation of adventitious buds or stimulates dor- 

 mant buds, especially those not too far distant from the central trunk, since 

 the upward force of the water and the nutrition is much more energetic in 

 a perpendicular direction than in the more inclined position. Gardeners 

 know how to turn this to use in growing plants on trellises. The horizontal 

 branches on one side of the mam trunk, which are weaker than the corres- 

 ponding ones on the other side, are held in a perpendicular position for a 

 year. This treatment results in a much greater and more rapid growth 

 and development. With the production of water shoots a gradually in- 

 creasing inequality in nutrition sets in, at the expense of the older, more 

 horizontal branches which now suffer from scarcity of nourishment. This 

 explains the death of the tip twigs of older lateral branches which begins 

 with the appearance of the water shoots. One part of the tree starves when 

 some other part develops very luxuriantly. 



As has been said, it is scarcely advisable to remove the water sprouts 

 during such a disturbance in the equilibrium of nutrition, rather, it is more 

 advantageous in older trees to graft them with valuable varieties and, at 

 the same time, to saw ofif a part of the older branches, so that the tree is 

 thus rejuvenated. In places where the sub-soil cannot be opened up easily 



Sorauer, P., tjber Rosenkrankeiten, Zeitschr. f. Pflanzenkrankh. 1898. p. 220. 



