444 



SOT ANY. 



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 longtime for the formation of a broad bud or growing 

 point (punctumvegetationis), and afterward push up a cylin- 

 drical stem in which little change subsequently takes place. 



In the Dragon trees 

 (Draco? na, sp.) and 

 tome other Monoco- 

 tyledons, there is a 

 thick layer of paren- 

 chymatous cortex be- 

 tween the column of 

 fibro- vascular bundles 

 and the epidermis 

 (Fig. 322, r), and in 

 the deeper layers of 

 this a persistent meri- 

 stem tissue is found 

 (Fig. 322, .r). 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 

 stems increase in 

 thickness there always 



, meristem zone of the fundamental system in i i i 



^yhich new bundles and tiseues are forming.-After develops SOO11 a layer 



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 t'ascicn- 



Fig. 322. Cioirs-section of f>tem of Draccenu. e, 

 epidermis ; k, cork ; r, cortex ; 6, a flbro vascular 

 bundle bending out to a leaf ; , parei chyma of the 

 fundamental system ; g, g, flbro-vjiseular bundles ; 



