[331] 



SCIENTIFIC MANUAL. 



46 



manifest, save that the rudimentary flowers and fruit are 

 enclosed within the leaves, and may often be seen plainly 

 on cutting the bud open." (Johnson's How Crops Grow.) 



The stem as naturally ascends, 

 seeking light and air, as the root 

 descends and spreads in the soil, in 

 search of food. 



Plants are divided, as regards 

 their stems,into two general classes : 

 endogens (Fig. 7), or monocatyledonous 

 plants, and exogens, or dicatyledon- 

 ous plants (Fig. 8). 



Endogens embrace all of those 

 plants whose stems grow from the 

 inside, which, at germination, have 

 only one seed-leaf, and which put 

 forth a number of roots from the 

 base of the seed. 



To this class belong the cereals, 

 grasses, palms, etc. An other ^pe- 

 culiarity of these plants is, 

 that the bark cannot be 

 separated from the wood, 

 and that the outside hard- 

 ens while the centre is yet 

 soft. 



Exogens embrace those plants whose stems'increase by 

 successive layers or rings next to the bark, have at ger- 

 mination two seed-leaves, and extend into the soil a ver- 

 tical tap-root, from which lateral roots branch out *with 

 more or less regularity, dependent somewhat upon^the pul- 

 verulent condition of the surrounding soil. A large ma- 

 jority of plants, shrubs and trees is embraced in this class, 

 especially in higher latitudes. 



The stems of endogens are composed of ' ' separate bun- 



