1. Longitudinal section of the cortical parenchyma of celandine root (Chelidonium majus, L.)
2. Cross-section of the cortical parenchyma of sarsaparilla root (Smilax officinalis, Kunth).
PLATE 52
A. Longitudinal section of the pith parenchyma of grindelia stem (Grindelia squarrosa, [Pursh] Dunal).
1. Cell cavity.
2. Cross-section of the porous end wall.
3. Surface view of the porous side wall.
B. Cross-section of the pith parenchyma of grindelia stem.
1. Cell cavity.
2. Porous walls.
3. Pitted end walls.
LEAF PARENCHYMA
The parenchyma cells (Plate 109, Fig. 1) of leaves, of flower petals, and the parenchyma cells of some aquatic plants are branched; that is, each cell has more than two cell terminations. These cell terminations are frequently quite attenuated and usually very blunt. Such a cell structure provides for a greater amount of intercellular space and a maximum exposure of surface. This arrangement makes it possible for the parenchyma cells of the leaf to absorb more readily the enormous amount of carbon dioxide needed in the photosynthetic process.
AQUATIC PLANT PARENCHYMA
The parenchyma of aquatic plants (Plate 59) has large intercellular spaces formed by the chains of cells.
WOOD PARENCHYMA
Wood parenchyma (Plate 105, Fig. 3) cells are the narrowest parenchyma cells occurring in the plant. Their walls are always lignified and strongly pitted, and in some cases the end walls common to two cells are obliquely placed.