DICOTYLEDON ES 



405 



While among the Monocotyledons, at least outside the Tropics, 

 trees are rarely found, the Dicotyledons are very often arborescent ; 

 and, except for those regions where the Conifers predominate, make 



FIG. 383. A, Ricinus communis, cross-section of hypocotyl, showing the arrange- 

 ment of the primary vascular bundles (X 6). B, Tilia Americana, section of a 

 branch, showing six annual growth rings (X4) ; cor, cortex; ph, phloem; a;,xylem; 

 m, pith ; i.e., interfascicular cambium ; pm, primary medullary ray. 



up the greater part of the forests. Dicotyledons are, as a rule, more 

 gregarious than the Monocotyledons. The few types of the latter, 

 like the Grasses and some aquatic forms (Typha, Scirpus, etc.), often 



B 



FIG. 384. A, Tropseolum majus, cross-section of vascular bundle from the stem; 

 no cambium is present. B. Pelargonium sp., cross-section of stem-bundle, show- 

 ing cambium, cam (x 200). en, endodermis; ph, phloem; , sieve-tubes; xy, 

 xylem ; t, vessels. 



grow in large masses, but, aside from these, the plants which give 

 the special character to the flora of most temperate regions are, with 

 the Coniferae, the Dicotyledons. 



