Page:The Oak.djvu/57

 CHAPTER IV.

(continued).

proceed to describe the chief features of importance in the structure of the shoot of the young oak-plant, premising that many of the remarks may here be curtailed in view of the facts already learned in connection with the root. The first object will be to bring out the differences in the shoot as contrasted with the root, and first we may examine the structure by means of transverse sections as before. The shoot consists of all the structures developed from the plumule.

Such sections show that we have here also various definitely grouped tissues, of which we may conveniently distinguish three systems. A series of vascular bundles grouped in a close ring constitutes one of these systems; another is represented by a single layer of cells at the periphery of the section, and this is called the epidermis; and the remainder of the section composes the third system, often termed the fundamental tissue, and divided arbitrarily into three regions—the pith, the cortex, and the primary medullary rays (Fig. 9). The