138 



THE ESSENTIALS OF AGRICULTURE 



171. A study of the corn plant. The stem or stalk of the 

 corn plant ranges from two to twenty feet in height. The outer 

 covering of the stalk is hard and smooth, giving strength to the 

 stem. The stem is not hollow like wheat and oats, but is filled 

 with soft, spongy pith. Distributed through the pith are the 

 circulatory ducts which carry water and food solutions from the 

 roots to the other parts of the plant, and also distribute the or- 

 ganized food from the leaves to the growing parts of the plant. 



The male flowers are 

 borne at the top of the 

 stalk in the tassel, and 

 the female flowers on 

 the cob (Fig. 16). An 

 average tassel contains 

 as many as thirty mil- 

 lion yellowish dustlike 

 particles, called pollen 

 grains, which are blown 

 about by winds, some 

 of them lodging on the 

 moist ends of the silks, 

 where they germinate. 

 The pollen from one 

 plant usually blows to 

 the silks of other plants, 

 giving what is known as cross-pollination (Fig. 60), which re- 

 sults in cross-fertilization. 1 It is this fact that causes mixture of 

 colors and other characteristics in corn, and makes it difficult to 

 keep varieties pure when growing in adjoining fields. In plants 

 such as corn, which are naturally cross-fertilized, this crossing 

 is necessary to maintain vigor. 



172. How and when to prepare the seed bed. To supply the 

 most favorable conditions for germination and growth, the 

 ground should be plowed from five to eight inches deep, should 



1 For discussion of fertilization in seed plants, see Bergen and Caldwell's 

 " Practical Botany " or " Introduction to Botany." Ginn and Company. 



FIG. 60. Results of poor pollination 



When scanty pollination occurs, few ovules are fer- 

 tilized and few kernels develop 



