Wood parenchyma, particularly of the older wood, function as storage tissue. The wood parenchyma of quassia, like the wood parenchyma of most woods, contain stored products. In some cases the wood parenchyma contain starch, in others crystals, and in others coloring matter, etc.
PLATE 65
1. Stone cells with starch of Ceylon cinnamon (Cinnamomum ceylanicum, Nees.). 2. Stone cells with solitary crystals of calumba root (Jateorhiza palmata, [Lam.] Miers). 3. Parenchyma cells, with starch of cascarilla bark (Croton eluteria, [L.] Benn.). 4. Cortical parenchyma with starch of sarsaparilla root (Smilax officinalis, Kunth). 5. Cortical parenchyma, with starch of leptandra rhizome (Leptandra virginica, [L.] Nutt.). 6. Crystal cells, with solitary crystals of quebracho bark (Schlechtendal). 7. Bast fibre of blackberry root with starch (Rubus cuneifolius, Pursh.).
PLATE 66
Mucilage and Resin
1. Cross-section of elm bark (Ulmus fulva, Michaux) showing two cavities filled with partially swollen mucilage.
2. Mucilage mass from sassafras stem bark (Sassafras variifolium, L.).
3. Mucilage mass from elm bark.
4. Resin mass from white pine bark (Pinus strobus, L.).
In many plants, however, the parenchyma cells contain crystals. The parenchyma cells of rhubarb contain rosette crystals, while the parenchyma cells of the cortex of sarsaparilla and false unicorn root contain bundles of raphides. In every case observed the raphides are surrounded by mucilage. This is true of squills, sarsaparilla, false unicorn, etc. When cells with raphides and mucilage are mounted in a mixture of alcohol, glycerine, and water, the mucilage first swells and finally disappears.
STORAGE CAVITIES
Particular attention should be given to storage cavities whenever they occur in plants, for the reason that they are usually filled with storage products, and for the added reason that storage cavities are not common to all plants. Storage cavities occur in roots, stems, leaves, flowers, fruits, and seeds.