. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. FIG. 69.—Cross section of a portion ofthe blade of a leaf, showing upper epidermisat a, lower epidermis at b, palisade paren-chyma at c, spongy parenchyma at d, andtracheids from the end of a vein at e. 140 CONSTRUCTION OF PLANTS FOOD. Food-building Apparatus.—It is the special business ofleaves to make the food, and there the palisade and spongyparenchyma are the tissues directly concerned in the work (), since the new food makes its appearance first in individua
. Plant anatomy from the standpoint of the development and functions of the tissues, and handbook of micro-technic. FIG. 69.—Cross section of a portion ofthe blade of a leaf, showing upper epidermisat a, lower epidermis at b, palisade paren-chyma at c, spongy parenchyma at d, andtracheids from the end of a vein at e. 140 CONSTRUCTION OF PLANTS FOOD. Food-building Apparatus.—It is the special business ofleaves to make the food, and there the palisade and spongyparenchyma are the tissues directly concerned in the work (), since the new food makes its appearance first in individual cellof these tissues is therefore a food-buildingunit, and the factors concerned in food synthesis can be fol-lowed out in seeing how one of these cells does its work, namely, how it obtains the raw materials and the sunsenergy, how the arrested energy of the sun isutilized, how the finished product is disposedof, and how the apparatus of the cell is keptin working order. The Chloroplasts.—The chloroplasts () are plastids that contain the green pig-ment chlorophyll (see page 8). They arethe organs of the cell that are directly con-cerned in food-construction from carbondioxide and water. This is known from thefact that this process does not go on wherechloroplasts are absent; and where starchis formed, as is nearly always the cas
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