272 Internal Modifications 



pers. In consequence of this great apparent deviation from the 

 usual structure, a celebrated Swedish botanist has remarked 

 that grasses are the least endogenous of all endogenous plants. 

 But if the gradual development of a grass be attentively ob- 

 served, it will be found that the stem was originally solid • 

 that it then becomes hollow in consequence of its increasing 

 in diameter more rapidly than new tissue can be formed ; and 

 that finally in old arborescent stems it again becomes solid by 

 the constant addition of new matter to its inside ; so that its 

 deviation from the ordinary characters of endogenous structure 

 is much less considerable than it seems to be at first sight. The 

 embryo, of all plants that have these kind of stems, bears only a 

 single cotyledon or seed leaf, and hence endogens are called 

 Monocotyledonous Plants. Parallel veined or nerved leaves 

 are also characteristic of this kind of plant Fig. 8, Section of a 

 woody stem of three years' growth, i, h, first year's growth and 

 hardest part of the wood ; h, g, second year's growth ; g, b, third 

 year's growth or sap wood formed from the cambium ; a b is 

 the bark, b i, the wood ; i k, the pith ; a c. cuticle, or disorgan- 

 ized part of the bark ; c d, cellular integument ; d b, cortex ; j e, 

 medullary rays. Fig. 7, A palm, a b, woody fibre most dense 

 and hard ; b c, less numerous and compact ; c d, very few, mostly 

 cellular tissue. The small figures a a, are the natural size ; the 

 large ones, B B, much magnified to show the structure. 



fMoUifled from Lin<il«jr i 



Lombardy Poplars. — These beautiful trees arc easily propa- 

 gated, and simply by thrusting the limbs of healthy trees into the 

 soil in the early spring, or late in fall. We have many now in 

 a very vigorous state, propagated in this way. The Balm of 

 Gilead, and the various kinds of willow, require only to be stuck 

 into the soil to insure a successful growth. The soil need not 

 be over moist. 



