132 PRINCIPLES OF PLANT CULTURE 



plants grow narrow, and are thick, fleshy and wrinkled. 

 If the plants are pulled sufficiently to break the tap-root, 

 before the disease has progressed too far, they often re- 

 cover. 



223. Water-sprouts (sap-sprouts, gormands) on fruit- 

 trees are sometimes due to an excess of water in the soil. 

 These thick, rapidly-growing shoots, with remote leaves 

 and poorly-developed buds, growing from the main 

 branches of unthrifty fruit-trees, are most common on 

 undrained, heavy soils. They rarely produce much fruit, 

 but tend to rob the bearing branches of light and nourish- 

 ment. They usually continue to grow late, and in severe 

 winters are often injured by cold. Water-sprouts may also 

 result from over-pruning and from injury of the tree by 

 cold, but in the absence of these conditions they suggest 

 the need of drainage. 



224. Cracking. Fruits and vegetables often crack 

 from excessive moisture, either through too much absorp- 

 tion by the roots or by direct absorption through the skin. 

 Cracking is most frequent after heavy rains following 

 drought. Apples, tomatoes, melons, carrots, kohlrabi, 

 cabbage and potato tubers are subject to it. On wet 

 soils, drainage may largely remedy the evil. The selection 

 of varieties least subject to cracking is also helpful, es- 

 pecially in melons and tomatoes which often crack in 

 comparatively dry weather. In these cases the cracking 

 is probably due to an unequal maturing of the fruit, which 

 causes certain parts to grow faster than others. The 

 bursting of cabbage heads is due to the excessive absorp- 

 tion of water by the roots. To prevent it, we start the 

 plants by pulling on the stem sufficiently to break a part 

 of the roots. 



225. Knobby potatoes are caused by a wet period 



