444 



BOTANY. 



bundles are more numerous. In such a stem it is evident 

 that there can be no considerable increase in thickness after 

 it is once formed, and we consequently find that palms 

 take a long time for the formation of a broad bud or growing 

 point {2mnciu7ri vegetationis), and afterward push up a cylin- 

 drical stem in which little change subsequently takes place. 



In the Dragon trees 

 (Dracmia, sp. ) artd 

 some other Monoco- 

 tyledons, there is a 

 thick layer of paren- 

 chymatous cortex be- 

 tween the column of 

 fibro-yascular bundles 

 and the epidermis 

 (Fig. 322, r), and in 

 the deeper layers of 

 this a persistent meri- 

 stem tissue is found 

 (Pig. 322, x). In this 

 meristem there are 

 formed fibro-vascular 

 bundles, which lie par- 

 allel to those already 

 formed, and in this 

 way the stem slowly 

 increases in thickness. 

 545. — In those Di- 

 cotyledons whose 



Fig. 323. — Cross-sectioB of ptem of Draccena. e, , 



epidermis ; k. corlt ; )■, cortex ; b, a flbro-Tasciilai- StCmS increase lU 



bundle bending out to a leaf ; m, pareuchyma of the , -i • i , i i 



fundamental system ; g, g, fibro-vaecular bundles ; tUlCKneSS there always 



ip, meristem zone of tne fundamental system in ^rt,r«i^,-.Q c!^^« o Ioxt^i. 



■whicli new bundles and tissues are forming.— After ueveiops SOOn a layei 



®'"^''^' of meristem tissue, 



which connects the cambium layer of one fibro-vascular 

 bundle with that of the other (Fig. 323). This is made 

 easier from the fact that in most (but not all) Dicotyle- 

 dons the bundles lie at nearly the same depth beneath the 

 epidermis on all sides of the stem, thus forming a cylinder, 

 or in cross-section, a ring, as in Fig. 323. Both the fascicu- 



