PLANT REPRODUCTION 107 



originated in this manner. Bud mutants are also occasion- 

 ally produced. 



Plant Breeding. — This is a branch of botany which has been 

 developed in recent years and has for its object the production of 

 new and valuable plants. It involves not only the selection of 

 valuable variations and mutations, but also the hybridization of 

 plants. In fact, hybridization may be considered the most im- 

 portant part of the work. It consists in the oross-pollination of 

 related plants and in the study of the resulting offsprings. It 

 is a very complicated subject and requires a special training to 

 insure success. 



LABORATORY EXERCISES. 



Exercise 1. Examine germinating pollen grains. 



Method: Fasten a glass ring to a slide with balsam; sterilize the slide, 

 ring and a cover glass. Boil a 10 per cent, sugar solution for a, few 

 minutes; put a drop on the cover glass by means of a sterilized wire; 

 inoculate with pollen, invert over the ring and examine in a few hours. 



Exercise 2. Examine prepared slides of ovules showing the one, two, 

 four and eight celled stages of the embryo sac. 



Exercise 3. Examine prepared) slides showing different stages of em- 

 bryo growth. Also note the endosperm, nucellus and integuments. 



