364 



The Living Plant 



continuously working embryonic tissues, plants are sharply dis- 

 tinct from animals, all of whose tissues sooner or later become of 

 the permanent kind, thus limiting their further growth. 



Although the most typical stems possess this remarkable 

 cambium system, there are others which lack it. In these the 

 further growth takes place by the addition of new fibrovascular 

 bundles, or veins, among and outside of the old ones, so that the 



Fig. 140. — Cross sections of stems of the two typical kinds, — endogenous with scattered 

 bundles (the Palm on the left), and exogenous with the bundles in rings (the Scotch 

 Fir on the right). The matter is further explained in the text. 



fully-grown stem is composed of separated bundles scattered 

 irregularly through the ground tissue, as well seen in the Corn, or 

 a Palm stem (figure 140, left), or any plants of the great clas- 

 sificatory division of the Monocotyledons. Observation alone, of 

 these stems, conveys the impression, though a false one, that the 

 new bundles originate inside of the old ones, whence they have 

 been described improperly as endogenous, in contrast with the 

 exogenous growth from cambium (figure 140, right). The growth 

 of exogenous stems involves matters of much interest, as figure 141 



