. Introduction to botany. Botany. Pig. 52. Top view of ver- tical shoot of syringa (PMladelphus) The leaves are arranged in pairs, and each pair over- lies the spaces hetween the pair immediately below it. One fourth natural size the fihrovascular bundles connecting it icith the stem. The im- portance of this is clear from what has akeady been said (sect. 37) about photosynthesis as a process of food-making in which the elements of water from the soil and of carbon dioxide from the air are brought together in the leaf to form sugar and starch. Have the veins of the leaf other uses besides thei
. Introduction to botany. Botany. Pig. 52. Top view of ver- tical shoot of syringa (PMladelphus) The leaves are arranged in pairs, and each pair over- lies the spaces hetween the pair immediately below it. One fourth natural size the fihrovascular bundles connecting it icith the stem. The im- portance of this is clear from what has akeady been said (sect. 37) about photosynthesis as a process of food-making in which the elements of water from the soil and of carbon dioxide from the air are brought together in the leaf to form sugar and starch. Have the veins of the leaf other uses besides their function as conveyers of water ? Explain. 69. Alternate and opposite arrange- ment of leaves. ^Mien a leafy apple twig (fig. 51) is compared with one of maple or box elder, it is evident that the former has its leaves arranged in a spiral order, while the latter bears its leaves in pairs. One leaf of each pair is on the opposite side of the twig from its mate, and a leaf of each pair covers the inter- val between the two leaves next above or the two leaves next be- low (fig. 52). Leaves borne in spirals are said to be alternate, and those in pairs, like maple leaves, are said to be opposite. The spiral arrange- ment is much the commoner, being char- acteristic of most herbs, most shrubs, and very many hard-wood and fruit trees. Some of the most familiar opposite-leaved. Fig. 53. Top view of a horizontal shoot from the shrub shown In figure 52 The leaves spring from the branch in the same order as do those of the vertical branch, but by a twisting of the leafstalks the blades are made to lie in a nearly horizontal position, and thus secure abundant illumination. One fourth natural size. 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 Bergen, Joseph Y. (Joseph Young), 1851-1917; Caldwell, Otis William, 1869-
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