. The anatomy of woody plants. Botany -- Anatomy. ANATOMICAL STRUCTURE AND CLIMATIC EVOLUTION 423 subject further we may point out that the organization of the trunks of trees in succeeding geological epochs indicates a gradual cooling of terrestrial climates which, when it became accentuated, gave rise to a marked variation in annual temperature, recorded ever more clearly in the progressively greater definition of the annual rings in later geological times. It is now necessary to correlate the climatic changes more in detail with the internal organiza- tion of the plastic stem organs of vasc
. The anatomy of woody plants. Botany -- Anatomy. ANATOMICAL STRUCTURE AND CLIMATIC EVOLUTION 423 subject further we may point out that the organization of the trunks of trees in succeeding geological epochs indicates a gradual cooling of terrestrial climates which, when it became accentuated, gave rise to a marked variation in annual temperature, recorded ever more clearly in the progressively greater definition of the annual rings in later geological times. It is now necessary to correlate the climatic changes more in detail with the internal organiza- tion of the plastic stem organs of vascular plants. It has been shown in Fig. 289, repre- senting the wood of the cordaitean Mesoxylon of Car- boniferous age from the north of England, that the only differentiation which marked annual increments of growth in this early age was a slight narrowing in radial diameter of the tracheids formed toward the end of the period of growth. No other structural feature related to the phenomenon of annual rings has been recorded as yet from either the late Paleozoic or from the early Mesozoic (Triassic). In the Jurassic, however, and practically universally from this epoch onward, a marked modification in the organization of the annual rings presents itself. This is well shown in the structure of the wood of Ginkgo (Fig. 293), a survivor of a stock which attained its zenith of development in the Mesozoic age. Clearly the tracheids which mark the termination of the annual increment differ from those previously formed in the character of their pitting. The. FIG. 292.—Transverse section of the wood of Agathis australis from New Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Jeffrey, Edward C. (Edward Charles), b. 1866. Chicago, Ill. , The University of Chicago Press
Size: 1585px × 1576px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookpublisherchicagoilltheuniversityo, booksubjectbotanyanatomy
