30 



PRINCIPLES OF PLANT BREEDING 



Stamens from the flower to be worked upon may be removed 

 with a pair of fine pointed scissors (Fig. 21). Care must be exer- 

 cised to not injure the pistil. This work must be done before the 

 pistil is ready to receive the pollen. 



Such flowers may be protected from receiving outside pollen 

 by tying a paper bag over the stem supporting the blossom 

 (Fig. 22). Natural development will take place within the paper 



FlG. 22. ToSacco field showing bagged plants in seed breeding plots. (U. S. D. A.) 



bag. After the pollen growth has reached the ovules in the pistil 

 there is no longer any danger of outside pollination. Then the 

 bag may be removed. 



During the cross-pollinating of flowers it is necessary to place 

 labels on the stems. This should indicate both the staminate and 

 pistillate parents. Records should also be kept of all such cross- 

 ing. Numbers or letters may be used to designate the different 

 parents, These are often written above and below a horizontal 

 line, the staminate number being above the line and the pistillate 

 below, thus: 



325 

 157 



The study of flowers and their cross-pollination may be carried 

 on during the winter by placing several branches from fruit trees 

 in a jar of water in a warm room for several days before the study 

 is made. If the conditions be favorable the blossoms will develop 

 in a week or two. Let the several steps mentioned in the above 

 paragraph be tried on these flowers. 



Testing for Purity of Type. When a new strain of plants or 

 animals has been formed, through crossing or otherwise, the 



