PART II. 



INTERNAL MORPHOLOGY (ANATOMY). 



CHAPTER IX. 

 THE PLANT CELL: CELL-DIVISION: TISSUES. 



I. In the preceding chapters we have been concerned with 

 the larger external features of the bodies of flowering plants. 

 It is now necessary to study the internal and minute structure 

 of root, stem, leaf and flower in order that the physiology, or 

 the work which each of these organs carries on may be satis- 

 factorily understood. 



2. A knowledge of the internal structure is obtained by cutting 

 thin slices of the various organs with a 

 " sharp razor, and examining these slices or 

 -B sections as they are called with the naked 

 eye and with the microscope. For a 

 complete understanding of the nature and 

 relationship of the several internal parts 

 of any plant organ, it is not sufficient 

 to examine a section through it in one 

 direction only : sections must be made in 

 several directions. In stems, roots, and 

 other parts, which are longer than broad, 

 it is usual to make sections in the manner 

 indicated in Fig. 47. Those cut at right 

 angles to the main axis as at C, are 

 termed transverse sections; those which are cut parallel to 



the main axis are longitudinal sections, the terms radial and 

 104 



Fig. 47. 



