MOUNTAIN LAUREL
Epidermis. The epidermal cells of mountain laurel are occasionally modified, as unicellular hairs (Plate 110, Fig. 1), particularly in the region of the veins. The ordinary epidermal cells have thick outer walls and thin inner walls. Beneath many of the epidermal cells are large air-spaces.
Upper Palisade Parenchyma. The palisade parenchyma vary from four to five layers. The inner palisade cells are shorter and broader than the outer layer of cells.
Parenchyma. The parenchyma cells (Fig. 4) are rounded in form and they are arranged in the form of columns which are one cell in thickness above, but two to three cells in thickness near the under epidermis. Between each chain of cells is a larger intercellular space (Fig. 6). In a few of the cells are large rosette crystals.
Under Epidermis. The under epidermal cells are uniformly smaller than the upper epidermal cells.
It is thus seen that mountain laurel leaf has no hypodermal cells; no spongy parenchyma; no under palisade cells; no under hypodermal cells, and no secretion cavities.
TRAILING ARBUTUS
Epidermis. The epidermal cells of the trailing arbutus (Plate 111, Fig. 2) are variable in size. Many of the cells are modified, as guard cells (Fig. 1).
Parenchyma. The parenchyma cells are round and they are compactly arranged (Fig. 3) on the upper side of the leaf, but on the under side they are arranged in round, small, intercellular spaces (Fig. 5). In some of the intercellular spaces are rosette crystals (Fig. 7).
Under Epidermis. The under epidermal cells are smaller than the upper epidermal cells.