In Plate 101-A is shown the cork formation or secondary growth as seen in the older, larger buchu stems. The wavy epidermis (1), which is the primary epidermis and which has disappeared on many portions of the stem, has thin side walls and dark cell contents (2). Next to the epidermal cells occur several rows of peculiarly arched cork cells with thick, white outer walls (3) and reddish-brown cell contents (4). The cork cambium (5) is typical in form, and it has formed one or two layers of phelloderm cells (6) which have the same form as the cambium cells but with thicker walls. Next to the phelloderm occur the cortical parenchyma cells. The remaining structure of the mature stem is identical with that of Fig. 2. [Illustration: PLATE 100 CROSS-SECTION OF BUCHU STEMS (_Barosma betulina_ [Berg.], Barth, and Wendl.) 1. Hairs. 2. Wavy epidermis. 3. Cortical parenchyma. 4. Secretion cells and cavity. 5. Group of bast fibres. 6. Sieve cells. 7. Medullary rays. 8. Phloem parenchyma. 9. Vessels. 10. Wood fibres, and wood parenchyma. 11. Pith parenchyma.] [Illustration: PLATE 101 _A._ Cross-section of buchu stem (_Barosma betulina_ [Berg.], Barth. and Wendl.). 1, Outer wall of epidermis; 2, Cell cavity of epidermal cell; 3, Wall of cork cell; 4, Cavity of cork cell; 5, Phellogen layer; 6, Divided phellogen cell changing into a cortical parenchyma cell; 7, Cortical parenchyma cell. _B._ Cross-section of leptandra rhizome (_Leptandra virginica_ [L.], Nutt.). 1, Parenchyma cells undergoing change in the composition of their walls; 2, A break in the epidermal tissue; 3, Parenchyma cells undergoing division.] POWDERED BUCHU STEM