a4 THE CEREALS IN AMERICA 



the adults cannot be afforded. Indeed the number of sires that 

 are to be found in the upper end of the curv-e is so small that 

 the sires are apt to be but little if any better than the average. 

 In the breeding of animals in practice it is the few inferior 

 animals represented by the lower end of the curve that are dis- 

 carded. In the case of plants, however, embryo plants (seeds) 

 are produced in such abundance and at so small expense that 

 only the few at the upper end of the curve which are distinctly 

 superior need be saved. Instead of discarding the poorest ten 

 per cent, as in the case of animals, only the best five, or even 

 one, per cent may be saved in the case of plants. 



Practicums. 



47. To Demonstrate the Law of Variation from Type. — Take one 

 hundred ears of maize of one variety. Take weight of each ear in grams, or oimces, 

 and mark with gum label. Arrange ears in order of weight. Furnish each student 

 with a sheet of cross section paper, five inches square, with twenty sections to the 

 inch, or five by ten inches, ten sections to the inch, and have each plot the curve 

 indicated by the weight of the hundred ears. If necessary to save time, the 

 instructor may have ears weighed and marked in advance of the class exercise. 

 Variations in the length of one hundred ears may be shown in the same %\ay. 



Variation in the weight of grains of wheat may be sho\vn if facilities for 

 accurate weighing are at hand. The larger the number of grains used the better. 



48. Organs of Reproduction. — In order to become familiar with the floral 

 parts of wheat and other cereals, furnish each student with several heads of wheat 

 in different stages of inflorescence: 



1. Describe ovulary and state changes in size at different stages of maturity. 



2. Describe stigmas, state number of styles and position at various stages of 

 maturity. 



3. Describe length and position of filaments at different stages of maturity and 

 note manner and mode of attachment of filament to anther. 



4. Describe method by which anthers open and discharge their pollen. De- 

 scribe the pollen grain. 



For a portion of this work a high power microscope will be desirable. A two- 

 inch, two-thirds-inch and one-sixth objectives will be found suitable. With a large 

 :lass specimens may be prepared by the instructor and placed under one or more 

 ■microscopes and each student allowed to make examination by turn. 



To show that rye is cross-fertilized, while wheat is generally self-fertilized, a 

 similar study of rj'e may be made. The large anthers and abundant pollen of the 

 rye will be found to be the most striking contrast. 



