Page 50 – Boundry between water-storage tissue and mesophyll
Fig. 43 . Boundry between water-storage tissue and mesophyll. Sections of the chlorophyllaceous region of fully developed leaves to show the boundry between the lowermost layers of the water-storage tissue and the uppermost layers of the mesophyll. The former occupies the adaxial, the latter the abaxial side of the leaf. Notice the rather sharp almost straight boundry line between the two tissues (the more usual type), in A, as contrasted with the type where the mesophyll cells form projecting points into the water-storage tissue, as in B. Also notice the palisade cells, which usually constitute the uppermost row, or rows, of the mesophyll, in A and C, which are sometimes absent, as in B. The globose cells shown in B form the greater portion of the (unspecialized) mesophyll. In C, two fibers from a fiber-strand located near the boundry are shown (their walls stippled). The first row of mesophyll (palisade) cells constitutes the parenchymatous sheath of the strand. (A and C, longitudinal sections; B, transverse section). X100.