240 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 8B). 
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- 
MUU EL 
i HIRI 
Fia. 135.—Cross-sections of tree-trunks. A, of a Palm; B, of an Oak; lg, 
woody, and ec, cortical (bark), portion; m, pith; rm, 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. 
Practical Studies.—(a) Make cross-sections of young stems of the 
asparagus and hickory. Note the difference in arrangement of the 
bundles. In like manner compare cross-sections of young stems of 
virgin’s-bower (Clematis) and green-brier (Smilax). 
(d) Make vertical sections of the foregoing, and note the relation 
of the bundles to the leaves. 
(c) 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 
