2 BOTANY OF CROP PLANTS 



transpiration, etc., while the flowers which produce seeds, 

 carry on, for the most part, the reproductive activities, and 

 thus preserve the hfe of the race. However, we know that 

 many seed plants, such as potatoes, asparagus, cane fruits, 

 strawberries, and others may be propagated by using vege- 

 tative parts of the plants. 



The above classification has a physiological basis. 



We may also divide the seed plant body into two systems 

 on a structural basis, as follows : 



1. Shoot system, including stems, leaves, flowers, fruit and* 

 seed. The stems may be in the air {aerial) or underground; 

 the leaves may be ordinary foliage leaves, floral leaves (flower 

 parts) , or scale leaves. 



2. Root system, which may be in the soil, the water or air. 

 The roots, stems, leaves and flowers are not always typical, 



but may be modified or disguised, in some cases to such an 

 extent as to be scarcely recognizable. For example, the 

 tendril of the sweet pea is a leaf part, morphologically; the 

 potato tuber, a modified stem; the sweet potato, a modified 

 root. 



Size and Fonn of the Seed Plant Body.^ — There is a re- 

 markable variety of forms and sizes of seed plants in the 

 world. The duckweeds are very small, simple seed plants 

 floating upon the surface of ponds. They are without leaves 

 or with only very simple ones, they bear one or more rootlets, 

 and extremely small flowers which usually consist of a single 

 stamen or a single pistil. At the other extreme are the Giant 

 Sequoias of California; one individual, the General Sherman 

 "big tree," measures 279.9 f^^t in height and 102.8 feet about 

 the base. 



We commonly make a distinction between trees, shrubs and 

 herbs — plants which differ much in form and habit. Trees 

 and shrubs are woody, while herbs possess less woody tissue 



