106 BOTANY FOR BEGINNERS CHAP. 



diameter. Cut transverse sections and mount in water. Examine 

 under a low power. Note 



(i) The epidermis. 



(ii) The cortex. 



(iii) The vascular bundles, which are not united. 



(iv) The ground tissue between the bundles. 



(v) The cambium, between the phloem and xylein. 



EXPT. 98. Cut transverse sections from a stem of the Sunflower, 

 which is twice the age of the stem used in Expt. 97, and mount in 

 glycerine. Observe 

 (i) The vascular bundles, 

 (ii) The cambium ; see if a complete 

 ring is formed. 



EXPT. 99. Prepare a thin transverse 

 section from the stem of a full-grown Sun- 

 flower, which has been kept in spirit for 

 some time to remove the resin and air, 

 and to harden the tissues. Mount in 

 r b glycerine or glycerine jelly. Examine 

 under a low power, and note 



(i) The vascular cylinder, which is 

 formed by the union of the bundles. 



FIG. 132. Transverse section (ii) The pith, the cells of which have 

 of young stem of Wallflower. l ost t h e ir living contents. 



vtsculafbundles^C^coAet; (*) The lar g e multicellular hairs which 

 E, epidermis ; A, hair. project from the epidermis. 



EXPT. ioo. Cut a radial longitudinal 



section of the stem of the Wallflower, and mount in water. Examine 

 first under a low power then under a high power, and note 



(i) The epidermis. (v) The phloem. 



(ii) The cortex. (vi) The cambium, 



(iii) The endodermis. (vii) The xyleni. 



(iv) The pericycle. (viii) The pith. 



Growth in thickness of a Dicotyledonous Stem. 

 In those perennial plants which possess open vascular bundles 

 new additions are made to both the xylem and the phloem by 

 the cambium which is between them. The xylem increases in 

 size by additions to its outer surface, the phloem by additions to 

 its inner surface, the central portion of the cambium remaining 

 meristematic. Thus, every season new layers are produced, 

 but far more xylem is formed than phloem. The rings 

 which are seen in a cross section of the oak are produced 



