178 HORTICULTURE FOR SCHOOLS 



Procedure. Study various flowers for the purpose of becoming 

 familiar with their structure. Make diagrams showing the different 

 parts. Label all parts. Compare flowers of species of fruit-trees, note 

 any differences in their structure. 



EXERCISE II. Study of pollen-grains. 



Materials. Flower-buds from various fruit-trees; watch glasses or 

 petri dishes in which to dry anthers; microscope; glass slides and 

 cover-slips. 



Procedure. Collect some flower-buds, remove the anthers and dry 

 according to methods described in this chapter. Examine the grains 

 of various pollens by use of the microscope. Sketch typical grains, 

 making drawings large enough to show their shape. Store some pollen 

 for future use according to methods given in this chapter. 



EXERCISE III. Germination of pollen-grains and the study of their 

 tubes. 



Materials. Van Teighem cells, or materials for making the same 

 (see paragraph 262) ; sugar solutions; pollen-grains. 



Procedure. Mount some pollen-grains in hanging-drop cultures as 

 described in the text. Examine them from time to time in order to 

 observe the pollen-tubes of different lengths. Make drawings showing 

 some of the germinated grains with their pollen-tubes. Notice the 

 comparative size of grains, diameter and lengths of the tubes, and rates 

 of growth of the tubes in different varieties of pollen. The following 

 are a few suggestive species of orchard trees and bush-fruits from which 

 pollen may be obtained at the proper time: almond, apple, apricot, 

 European plum, Japanese plum, peach, pear, walnut, grape, raspberry, 

 blackberry, date palm. 



EXERCISE IV. Practice in emasculation of flowers. 



Materials. Fruit-trees in bloom. 



Procedure. Emasculate some blossoms when they have reached the 

 proper stage according to methods described in this chapter. Apply 

 some pollen to the stigmas. Notice how tightly the pollen sticks. 



EXERCISE V. Exercise to show the effects of self-pollination versus 

 cross-pollination on the setting of fruit. 



Materials. Fruit-trees in bloom; viable pollen of different varieties 

 of the species emasculated; tags, paper-bags, and string. 



Procedure. Select a variety, carefully emasculate, and bag the 

 blossoms on a number of branches. When the stigmas are receptive, 



