138 MONOCOTYLEDONS 



1. Its slender, cylindrical Stem, and the tuft of leaves with 

 which it is crowned, is so different from the appearance of other 

 trees that every one at once understands that thu Cocoanut 

 Palm belongs to a class of plants quite different from that which 

 most other trees belong to. 



2. Monocotyledons and Dicotyledons compared. — A general 

 comparison of the Cocoanut tree with, for instance, a Mango tree 

 will make the characteristic features of the new class, called 

 Monocotyledons, distinct and clear. Beginning with the root, 

 we find that the Mango tree has a thick and stem-like taproot 

 with numerous side-roots, whereas the root of the Cocoanut Palm 

 consists of many similar, thread-like or fibrous roots. 



The trunk of the Mango tree is stout, grows thicker and thick- 

 er as it grows older, and is, at a certain height, divided into many 

 branches. The stem of the Palm tree is slender, does not increase 

 in girth as it grows older, and never branches. The latter fact 

 explains why the stem need not grow in girth, for it has not to 

 bear such a great load as the Mango tree. An examination of 



the section of the stem will show that 



les in the wood- 

 ance of the stem 



'ic.-.^'.v^v;=%cv <"-^^-v.^-\ ^^ ^^'^^ " ---V... v.. o.xcks closely bound 



^:,^^^-^c:.'..^^^^^^ together (fig. 125). The outside of the 



I^K'^'^'V^c'^^'^'^/i'^'.^^fefy trunk is not covered with hark, but con- 



''^'^-i^'i^WS^!^^^'^^ ^ists only of the very hard outer layer 



of the wood itself. Young stems of 

 monocotyledons have an epidermis, /'. e., 

 Fig. 125. -Transverse section .^ ^1^^,^ cellular coating like that of leaves. 



of a rnonocotvledonous stem. r,-., i /> , > i i 



llie absence oi the bark proper suggests 

 that there is not such a thing as the cambium ring in the stem 

 of the Palm tree. The sap circulates in the fibro-vascular bundles 

 distributed throughout the stem. The cellular tissue — the })ith — 

 of the inner ])art is looser, and contains fewer vascular bundles 

 than tliat of the outer part, which, with its densely packed ring 

 of hiiiHlles, protects the inner i)art from damage, evaporation 

 and changes of temperature. Many plants of this class, e. ff., 

 the Bamboo and othor Drasses, have even hollow stems. 



