268 HOW CHOPS GROW. 



est herbaceous stems, while they constitute a large share 

 of the trunks of most shrubs and trees. From the tough 

 ness which they possess, and the manner in which they 

 are woven through the original cellular tissue, they give 

 to the stem its solidity and strength. 



The flowering plants of temperate climates may be di 

 vided into two great classes, in consequence rf important 

 and obvious differences in the structure of their stems and 

 seeds. These are, 1, Endogenous or Monocotyledonous 

 and, 2, Exogenous or Dicotyledonous plants. As regards 

 their stems, these two classes of plants differ in the ar 

 rangement of the vascular or w r oody tissue. 



Endogenous Plants are those whose stems enlarge by 

 the formation of new wood in the interior, and not by the 

 external growth of concentric layers. The seeds of endog 

 enous plants consist of a single piece do not readily 

 split into halves, or, in botanical language, have but one 

 cotyledon; hence are called monocotyledonous. Indian 

 corn, sugar cane, sorghum, wheat, oats, rye, barley, the 

 onion, asparagus, and all the grasses, belong to this tribe 

 of plants. 



If a stalk of maize, asparagus, or bamboo, be cut across, 

 the bundles of ducts are seen disposed somewhat uni- 



formly throughout the section, though less abundantly to 

 wards the center. On splitting the fresh stalk lengthwise, 

 the vascular bundles may be torn out like strings. At 

 the nodes, where the stem branches, or where leaf-stalks 

 are attached, the vascular bundles likewisj divide and 

 form a not-work, or plexus. In a ripe maize-stalk which is 

 exposed to circumstances favoring decay, the soft cell-tis 

 sue first suffers change an 1 often quite disappears, leaving 



