. Heredity and evolution in plants . nsi- of generations. The real reason is, tions from a one-celled to because the Pleurococcus protoplasma multi-cellular plant. possesses a physical and chemical (Cf. Fig. 34.) constitution—or m other words a mechanism—that, under normal external conditions,manufactures green pigment instead of red, cellulose in-stead of lignin, or any other substance, at the surface,and makes the cell-wall of even resistance to the osmoticpressure within, thus producing a sphere and not an ellip-soid, or filament, or any other shape. 38. What is Inheritance.—When the Pleuro
. Heredity and evolution in plants . nsi- of generations. The real reason is, tions from a one-celled to because the Pleurococcus protoplasma multi-cellular plant. possesses a physical and chemical (Cf. Fig. 34.) constitution—or m other words a mechanism—that, under normal external conditions,manufactures green pigment instead of red, cellulose in-stead of lignin, or any other substance, at the surface,and makes the cell-wall of even resistance to the osmoticpressure within, thus producing a sphere and not an ellip-soid, or filament, or any other shape. 38. What is Inheritance.—When the Pleurococcus celldivides, this wonderful, invisible mechanism—the certain HEREDITY 47 definite physical and chemical constitution—is transmittedto each of the daughter-cells; each, in other words, re-ceives Pleurococcus protoplasm. This protoplasm, withits definite organization, constitutes the inheritance. Thedaughter-cells do not inherit a spherical shape (as is evidentfrom Fig. 33), but a definite kind of protoplasm, cell-sap. FIG. 34.—Pleurococcus vulgaris. Sections of one-, two-, and four-celledplants, showing the nuclei and the large chlorophyll bodies (chb) to whichthe green color of the plants is due. In D, the larger chloroplast is shownin perspective. (Camera lucida drawings from a microscopic preparationby E. W. Olive.). (Cf. Fig. 33.) of certain osmotic properties, and surface cellulose of evenelasticity, so that, in surroundings uniform on all sides,a spherical shape must finally result. The shape is anexpression of the inheritance for the given different external conditions the expression mightbe different; but the inheritance would be the same. Thechlorophyll in the daughter-cells, immediately after cell- 48 AND EVOLUTION IN PLANTS division, is a direct inheritance, but the chlorophyll subse-quently manufactured, and the green color which it givesto the plant, are not inherited; they are expressions of theinheritance—which in
Size: 1501px × 1664px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, bookidheredityevol, bookyear1920
