. Plant life and plant uses; an elementary textbook, a foundation for the study of agriculture, domestic science or college botany. Botany. FUNCTIONS 227. That soil is best for crops which is loose enough to permit air to get into it, and yet compact enough to prevent water from leaving it too rapidly. Sand, for example, is excellent for aeration, but poor for holding water. Lack of drainage, as well as too great compactness of soil, interferes with the proper respiration of roots. Thus, by one means or another, all living cells of the plant receive the oxygen which they must have, and the lea
. Plant life and plant uses; an elementary textbook, a foundation for the study of agriculture, domestic science or college botany. Botany. FUNCTIONS 227. That soil is best for crops which is loose enough to permit air to get into it, and yet compact enough to prevent water from leaving it too rapidly. Sand, for example, is excellent for aeration, but poor for holding water. Lack of drainage, as well as too great compactness of soil, interferes with the proper respiration of roots. Thus, by one means or another, all living cells of the plant receive the oxygen which they must have, and the leaves are the organs through which it chiefly enters. When the plant is not actively at work, not so much oxygen is needed; plants which live through the winter without leaves appear to get along mainly with what oxygen is already in their tissues; so also with the living 'cells in seeds. As has been said, we know very little about respiration. We know that it appears to be principally a kind of oxida- tion, which means that it is a chemical change involving the use of oxygen and the giving off of energy. We know, of course, that without it no work can be accomplished by living things. We know that as work increases respira- tion increases. This you have noticed yourself when exer- cise gets you out of breath; the body has greater need for Fig. 80. — Cross section of the stem of water milfoil (Myriopkyllum), a submerged plant. Note the large and symmetrically placed air passages. Note that the vascular cylinder, indicated by v, is in the center, as in roots. Note that its cells are but slightly differentiated. This is common in plants which grow under water; they evi- dently do not need heavy cell walls in order to maintain an erect 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 Coulter, John G.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1913
