A UNIT IN AGRICULTURE 19 



C. PLANT PROPAGATION. 

 Propagation by Seeds 



1. Process of germination. 



(a) Absorption of moisture. 



(b) Chemical 'changes of compounds in the seed from 



insoluble to soluble substances. 



(c) The production of heat. 



2. Conditions of germination. 



(a) Vitality of seed. 



(b) Moisture. 



(c) Heat. 



(d) Air. 



3. Vitality of seeds conditioned by : 



(a) Maturity. 



(b) Age. 



(c) Size. 



(d) Kind. 



(e) Extremes of temperature. 



(f ) Eepeated germination. 



Exs. 28, 29, 30. 



4. Methods of production and preservation of most important 



seeds. 



5. Selecting seeds of different crops. 



6. Seed testing. 



(a) For germination (see Ex. 6). 



(b) For impurities. Ex. 31. 



7. Treatment of refractory seeds. 



(a) By freezing (hickory, oak, walnut, hazel, pear, apple, 



peach, plum, etc.). 



(b) By scalding (black locust, honey locust, Kentucky coffee 



bean). 



(c) By stratifying (berries, blackberry, strawberry, rasp- 



berry, rose). 



