428 Plant-Breeding 



(C) The record. The record should include a description of 

 each parent, giving particular attention to the contrasted 

 characters. Colors may be recorded by comparing with a 

 standard color chart. The female parent should always be 

 mentioned first. The record on the label should include 

 variety name or number of each parent, date of emascula- 

 tion, and pollination. (Name of worker can also be placed 

 on the label.) As far as possible reciprocal crosses should 

 be made. 



EXERCISE 11 



Embryological Studies from Slides showing Cell Division at Dif- 

 ferent Stages, Chromosomes, Pollen Mother-cells, Development 

 of the Embryo-sac, etc. 



Provide each student with a high-power microscope and mi- 

 croscopic slides mentioned above. Careful drawings of each slide 

 should be made. 



EXERCISE 12 



Study of Pollen Germination and Fecundation 



Materials. Fresh and preserved flowers showing structure 

 of carpels in cross and long section ; microscopic slides showing 

 growth and penetration of pollen tubes into ovary, fecundation, 

 etc. For study of germinating pollen, fresh pollen may be 

 germinated in sugar solutions of various strengths mounted in 

 the cells of hanging-drop slides. If this is done at the beginning 

 of the practicum, the germinated pollen will be ready for ex- 

 amination before the end of the period. 



Careful drawings of all stages observed should be made. The 

 drawings should show all the differences in the length and size 

 of the pollen tube in various degrees of concentration of the sugar 

 solutions. Note also the effect of temperature and other external 

 influences upon germination. 



