PARENCHYMA
The larger amount of plant tissue is composed of parenchyma cells. These cells vary from square to oblong, or they may be irregular and branched. The end walls are square or blunt, and the wall is composed of cellulose, with the exception of the wood parenchyma, which has lignified walls.
There are seven characteristic types of parenchyma cells: (1) cortical parenchyma, (2) pith parenchyma, (3) wood parenchyma, (4) leaf parenchyma, (5) aquatic plant parenchyma, (6) endosperm parenchyma, (7) phloem parenchyma.
PLATE 49
A. Cross-section of black Indian hemp (Apocynum cannabinum, L.).
1. Longitudinal section of a latex tube.
2. Cross-section of latex tube.
3. Parenchyma.
B. Cross-section of a part of black Indian hemp root.
4. Cross-section of a large latex tube.
5. Parenchyma.
PLATE 50
Latex Vessels
1. Radial-longitudinal section of dandelion root (Taraxacum officinale, Weber).
2. Cross-section of sanguinaria root (Sanguinaria canadensis, L.).
3. Cross-section of dandelion root.
Parenchyma cells, cortical, pith, aquatic plant, leaf, flower, and endosperm, conduct in all directions—upward, downward, and laterally. The direction of conduction depends upon the needs of the different cells forming the plant. The fluids pass from the cell with an abundance of cell sap to the cell with less cell sap. In this wall all cells are provided with food.