33fi PRACTICAL BOTANY 



(periclinal). The details of arrangement of the suc- 

 cessive walls may with advantage be traced by com- 

 parison of several preparations, and explained by 

 reference to Figs. 13 and 14. Since the superficial cells 

 are subject to repeated periclinal divisions, it is clear 

 that there is no definite layer of dermatogen : compare 

 this structure of the punctum vegetationis with that of 

 the lateral buds above mentioned. 



2. Note the leaf-sheaths, successively smaller to- 

 wards the extreme apex, and observe how they originate 

 by outgrowth and division of successive zones of cells 

 below the apex. 



3. Attention should also be paid to the mode of 

 origin of the lateral buds : a diligent comparison of 

 them in various stages of development will show that 

 they are not of endogenous origin, but are derived from 

 superficial cells lying immediately above the insertions 

 of the leaf-sheaths. These cells divide, and form the 

 young buds, which subsequently appear to be completely 

 overarched by, and embedded in, the tissue of the leaf- 

 sheath, and ultimately burst through it. 



4. It will be useful further to trace the development 

 of the several tissues, and to note their relations to the 

 apical cell and its segments. 



IX. Cut a series of transverse sections through a 

 bud : prepare and mount them as above directed, being 

 careful to keep them in their proper order of succession, 

 and with their upper side uppermost. 



Some of the sections will only have passed through the 

 upper parts of the leaf-sheaths, which will appear as con- 

 centric rings, with a structure similar to that already ob- 

 served (III.) : note that the leaves of successive whorls 



