236 INTRODUCTION TO GENERAL SCIENCE 



7. Farmers' Bulletin No. 44: 11-22. Fertilizing Material-- 



Plant Food. 



8. Farmers' Bulletin No. 181. Pruning, 

 a. 1402:72-73. The Food Material. 



6. 1402 : 74-84. The Making of Living Matter. 



c. 1603 : 41-42. Feeding from the Air. 



d. 1603 : 31-33. Feeding from the Soil. 



e. 1611 : 81-90. How the Plant Uses the Food it Makes. 

 /. 1612:44-51. How Plants Feed. 



171. THE PROPAGATION AND BREEDING OF PLANTS 



Propagation means the production of new individuals. 

 It may take place through the agency of roots, cuttings, 

 leaves, buds, grafts, and seeds. 



By plant breeding is meant the production of plants having 

 new characteristics, which may be unlike any of the ancestors. 

 Cross-pollination, accomplished and regulated by man, may 

 produce these new plants. After proper selection is made of 

 the plants having the desired characteristics, and these plants 

 are bred from, there can gradually be produced plants having 

 a certain feature, to any desired degree. Nature has done 

 the same, but since nature necessarily must depend to such 

 a great extent upon accidental cross-pollination, and since 

 many accidents may happen to the new plants, the results 

 have not been as rapid as when the work has been carried on 

 by man. Also, in nature, there has always been a survival 

 of the fittest; there is a continual fight for existence, and the 

 new plant may not be as well adapted to maintain its existence 

 as some of the older forms. With man, since it is the plant 

 that is desired, the environment is adjusted to it, and the new 

 species has the best chance of living. It must be remembered, 

 in the experiments with plants, that man merely directs the 

 course that nature would take if given opportunity; but by 



