. Introduction to structural and systematic botany, and vegetable physiology. Botany. 118 THE STEM. or less flattened by the pressure of the woody wedges, and they serve to keep up the communication between the pitia and the bark. 210. The First Tear's Growth of an exogenous stem accordingly con- sists of three principal parts, viz.: 1st, a central cellular portion, or Pith; 2d, a zone of Wood; and 3d, an exterior cellular portion, or Bark. These several parts are displayed in Fig. 189-191, as they occur in a woody stem a year old. 211. The Pith (ilfe- dulla) consists en- tirely of soft cellul
. Introduction to structural and systematic botany, and vegetable physiology. Botany. 118 THE STEM. or less flattened by the pressure of the woody wedges, and they serve to keep up the communication between the pitia and the bark. 210. The First Tear's Growth of an exogenous stem accordingly con- sists of three principal parts, viz.: 1st, a central cellular portion, or Pith; 2d, a zone of Wood; and 3d, an exterior cellular portion, or Bark. These several parts are displayed in Fig. 189-191, as they occur in a woody stem a year old. 211. The Pith (ilfe- dulla) consists en- tirely of soft cellular tissue, or parenchy- ma* (51), which is at first gorged with sap. Many stems ' expand so rapidly in diameter during their early growth, that they become hollow, the pith being torn away by the disten- tion, and its remains forming a mere lin- ing to the cavity. In the "Walnut and the Poke (Phytolac-. * In rare instances a few threads of woody tissue and vessels are found dis- persed tlirough the pith, presenting a somewhat remarkable anomaly. This occurs in Aralia racemosa, and more strikingly in Oxybaphus, Mirabilis or Tour-o'clock, and other Nyctaginaceas. FIG. 189- Longitudinal and transverse section of a stem of the Soft Maple {Acer dasycar- pum), at the close of the first year's growth ; of the natural size. FIG. 190. Portion of the same, magnified, showing the cellular pith, surrounded hy the wood, and that enclosed by tlie barli FIG. 191. More magnified slice of the same, reaxjhing from the bark to the pith : a, part of the pith ; 6, vessels of the medullary sheath ; c, the wood ; dd^ dotted ducts in the wood ; «, annular ducts ; /, the liber, or inner fibrous bark ; g, the cellular envelope, or green bark ; A, the corky envelope ; i, the skin or epidermis ; ^, one of the medullary rays, seen on the trans- verse Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and ap
Size: 1313px × 1902px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorgra, bookcentury1800, bookdecade1850, booksubjectbotany
