. Elementary principles of agriculture; a text book for the common schools. transparent, to allow thelight to reach the innertissues of the leaf, isimpervious to second layer is a tier of cellswhich support the cutin layer. Thisepidermis is very efficient in keepinthe water in the leaf. Onside of the leaf, and on bothof some leaves, there are many . -^^^cim^^m^small openings,to let the car-bon dioxid en- ^. „, „ x,. , . ^ , . , Fig. 21. Howtheyoungplant gets its food. In the earlyter and the stages it is nourished from the store of food in the cotyledons. When the green leaves unfold
. Elementary principles of agriculture; a text book for the common schools. transparent, to allow thelight to reach the innertissues of the leaf, isimpervious to second layer is a tier of cellswhich support the cutin layer. Thisepidermis is very efficient in keepinthe water in the leaf. Onside of the leaf, and on bothof some leaves, there are many . -^^^cim^^m^small openings,to let the car-bon dioxid en- ^. „, „ x,. , . ^ , . , Fig. 21. Howtheyoungplant gets its food. In the earlyter and the stages it is nourished from the store of food in the cotyledons. When the green leaves unfold to theexcess of OXy- M&y^t they absorb the energy of the sunlight and cause the water to combine with the carbon dioxidgen pass out of ^^^ ^^^ to form starches and other foods. when the plant is making food. (Fig. 21.) Some waterescapes through these openings, or stomata (singular,stoma); but at night, when the food-making processesare not going on, these stomata close up, so thatmuch less water escapes. 47a. To get an idea of how well the epidermis protects the. 30 Elementary Principles of Agriculture plant, take an apple or potato and peel off the epidermis and placein an exposed place beside an unpeeled specimen Note how quicklythe peeled specimen will shrivel and dry, while the other retains itsform. 48. Carbon Assimilation. The soft tissue between theupper and the lower epidermis is the real food factoryof the plant. It is composed of several layers of cells,all arranged sponge-Hke, so that the carbon dioxidof the air can reach every celL All these cells containminute green bodies, called chloroplastids (chlo-ro-plast-ids). The green coloring matter in these bodiesis formed only in the light. It does not form in leavesgrowing in the dark. The yellowish stems of potatoesgrowing in dark cellars is a familiar example. The greencolor will disappear if plants are kept from the is taken of this property in blanchingcelery. When the Hght shines on the leaves,
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectagriculture, bookyear
