IMPROVEMENT OF PLANTS 161 



plants when exposed to the open lighted sky to assume a hori- 

 zontal position or one at right angles to the source of light (The 

 leaves of plants in the house having a side illumination only are 

 usually turned with their upper surfaces toward the source of light 

 or perpendicular to the incidence of the rays of light.); (5) the 

 arrangement of the leaves in rosette form as seen in peppergrass, 

 sow thistle, English plantain, strawberry, common thistle, mullein, 

 and the dandelion. 



Variation by Pruning. An example of what may be accom- 

 plished in the way of variation through pruning is found in the 

 origination of the Burpee Bush Lima Bean. Professor Bailey 

 in Plant Breeding relates the following incident: About 1883 a 

 Mr. Palmer had practically his entire crop of white pole Lima 

 beans destroyed by cutworms. But one little plant out of this 

 number, which had been cut off about an inch above the grouno\ 

 put out a new growth, and finally developed three pods, each con- 

 taining one seed. The following year these were planted and two 

 dwarf plants resulted, from which was finally developed the bush 

 Lima bean as we have it to-day. This suggests that other plants 

 may likewise undergo considerable variation under pruning and 

 care. 



Object of Pruning. According to Professor Bailey the objects 

 to be sought in pruning are: (1) to modify the vigor of the plant; 

 (2) to produce larger and better fruits; (3) to keep the plant within 

 manageable shape and limits; (4) to regulate the quantity of 

 fruit borne by the plant, (5) to remove injured limbs or super- 

 fluous parts; (6) to facilitate spraying and harvesting; (7) to 

 facilitate cultivation; (8) to make the plant assume some desired 

 form. 



Method of Pruning. A great deal of injury is often done to 

 trees by careless pruning and improper treatment of the resulting 

 wounds. When the limb is to be removed entirely, it should be 

 sawed or cut off close to the body of the tree so that no projecting 

 stub will be left to prevent the proper healing of the wound. 

 When the stub is left, it causes the bark to die around it, and in 

 course of time when the stub rots out a cavity will be left in the 

 tree in which insects or plant growths will lodge and eventually 

 injure the tree. When decayed places are found in trees, it 



PRAC. AGRICUL. 11 



