340 



BOTANY. 



they soon become connected by a cambium-ring as in the 

 Gymnosperms. In the perennial species this gives rise to 

 a marked difference in the structure of the stem (Fig. 135, 

 A and B). 



509. The tissues of Angiosperms are the most varied 

 and highly developed of any in the vegetable kingdom. 

 Not only is every tissue abundantly represented, but each 

 one shows almost numberless more or less well-marked va- 



Fio. 135.— Cross-sections of tree-trunks. A, of a Palm; B, of an Oak; Ig, 

 woody, and ec, cortical (bark), portion; m, pith; rTJi, medullary rays. 



rieties. Moreover, the structures which they form, as the 

 solid (woody) parts of the stems, are of a higher order and 

 far more complex than those in any other groups of plants. 



Praetical Studies. — (a) Make cross-sections of yonng stems of the 

 asparagus and hickory. Kote the difference in arrangement of the 

 bundles. In like manner compare cross-sections of young stems of 

 vlrgin's-bower (Clematis) and green-brier (Smilax). 



(J) Make vertical sections of the foregoing, and note the relation 

 of the bundles to the leaves. 



(«) Make cross and longitudinal sections of the solid (woody) part 

 of a bamboo or green-brier stem, and compare with similar sections 

 of oak or hickory. In the latter note the pith, medullary rays, and 

 distinct bark, not present in the former. 



(d; In the sections of oak and hickory note the cambium-zone 



