62 



THE VEGETATIVE FUNCTIONS OF PLANTS 



general types of distribution will be recognized, repre- 

 sented respectively by the corn or the lily, and by the 

 castor-oil plant or the parsnip. 



61. Internal Structixre of the 

 Corn Stem.^ — In the corn stalk, 

 the fibro-vascular bundles are dis- 

 tributed thickly .and irregularly 

 through the fundamental tissue 

 (parenchyma) of the stem (Fig. 

 4S). They are somewhat more 

 numerous near the outer rind. 

 A longitudinal section shows the 

 bundles in side view, extending 

 through the stem. The corn stalk 

 represents a type of structure com- 

 mon to all grasses^ and closely 

 related plants, and commonly 

 called endogenous. In growth, the 

 new tissue originates (with few ex- 

 ceptions, e.g., Yucca) only at the 

 tip of the stem. As a rule, growth 

 in thickness results only by the en- 

 largement of cells already formed, 

 without involving the formation 

 of new ones. 



62. Internal Structure of the 

 Castor-oil Plant Stem. — A type 

 of structure quite different from 

 that of the corn stalk is illus- 

 trated in the stem of the castor-oil plant (Fig. 46) . Here 

 the fibro-vascular bundles (in the young stem) are 



' The Indian corn (maize) belongs to the family of Grasses (Gramineae). 



Fig. 45. — Fibro-vascular 

 bundles in a corn stalk {Zea 



.\fnys). 



