This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 Excerpt: ...network best seen in the so-called "skeleton leaf." This arrangement of the veins insures a supply of material for assimilative purposes to every part of the leaf, and also at once removes the assimilated material from the leaf to be utilized at once in other parts of the plant or to be stored up for future use. ...
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1891 Excerpt: ...network best seen in the so-called "skeleton leaf." This arrangement of the veins insures a supply of material for assimilative purposes to every part of the leaf, and also at once removes the assimilated material from the leaf to be utilized at once in other parts of the plant or to be stored up for future use. Although the points already enumerated show the higher development of the dicotyledonous over the monocotyledonous leaf, yet undoubtedly the greatest advance made by the leaves of the group under consideration is that connected with Fig. 28. Leaf of melon, a typical Dicotyledon, showing stalk or petiole, prominent anastomosing veins forming a network and projecting from the under surface, also the cut edge or margin. protection against both climate and living enemies. The former only will be considered at present. In Monocotyledons, the leaf, when once fully expanded, remains rigid and motionless, its working surface being constantly exposed to the chills of the night air and to the dust settling down and covering up its chlorophyll and stomata, for it will be remembered that leaves can only perform their most important function, that of assimilation, when exposed to light; hence it would be a great advantage if leaves could pack themselves up during the night when unable to work, and this point has been reached by many Dicotyledons. The leaves of many Dicotyledons are still rigid and incapable of protecting themselves by closing up at night or on dull days when the light is insufficient to enable them to perform their functions; but the vast majority are moving in this direction, the first indication of such a move being an indication of toothing along the margin. From the primitive phase of cut margin as illustrated by the cherry or appl...
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