CHAPTER XXXIV 



STRUCTURE OF STEMS AND ROOTS 



420. There are two main types of stem structure found 

 among flowering plant-, which have their differences 

 based upon the arrangement of the fibro-vascular bundles. 

 These types are endogenous and exogenous. 



421. endogenous stems. Plants with this form of 

 stem are the monocotyledons. The vascular bundles arc 

 irregularly scattered through tin fundamental tissui <>f the 

 stem ( Fig. 399), and arc qoI arranged In circles about a 

 common center. The bundles are not parallel with each 

 other and arc not <>f the same size throughout then- length. 

 Pig. LOO shows the direction often taken bj the bundles 

 in the stem. On the exterior there is either an epidermis 

 or a false rind. The only trees which have this kind ol 

 stem an- oatives of the tropics or of warm countries. The 



palm is one of them, and 

 t hese stems arc gomet imes 

 called t be palm t \ pe. In 



OUr <wn climate \\,- find 



many examples, such as 

 greeubrier, Indian corn, 

 asparagus, grasses, or 

 chids, iris, and cat - tail. 

 To study it mi 11 g( im n ( 

 h a inll, s in orn : Cut t Inn 

 sections of a Bmall coin 

 stem which has been pre- 

 served in alcohol. Stain with hematoxylin. Examine 

 with the low power, and make a sketch showing the 



Ainu 

 the scattered flbro \ oscular btu 

 Slightly enlarged, 



