62 
THE VEGETATIVE FUNCTIONS OF PLANTS 
general types of distribution will be recognized, repre- 
sented respective!^ by the corn or the lily, and by the 
castor-oil plant or the parsnip. 
61. Internal Structure of the 
Corn Stem. In the corn stalk, 
the fibre-vascular bundles are dis- 
tributed thickly and irregularly 
through the fundamental tissue 
(parenchyma) of the stem (Fig. 45). 
They are somewhat more numerous 
near the outer rind. A longitudi- 
nal section shows the bundles in side 
view, extending through the stem. 
The corn stalk represents a type 
of structure (monocolyledonous) 
common to all grasses 1 and closely 
related plants, and often, though 
misleadingly, called endogenous. 
Ingrowth, the new tissue originates 
(with few exceptions, e.g., Yucca) 
only at the tip of the stem. As a 
rule, growth in thickness results 
only by the enlargement 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 
1 The Indian corn (maize) belongs to the family of Grasses (Gramineae). 
FIG. 45. Fibro-vascular 
bundles in a corn stalk (Zea 
Mays). 
