. A text-book of botany for secondary schools. Botany. 24 A TEXT-BOOK OP BOTANY with definitely spaced lines, preferably five millimeters apart.* As the leaf continues to grow, the most active growing, region will be indicated by the lines that draw farthest apart. 17. Protection.—Such an important organ as the leaf, with its delicate active cells necessarily in communication with the air, is exposed to numerous dangers. Conspicu- ous among these dangers are drought, intense light, and cold. Many ways of meeting these dangers have been developed by plants, but the subject is too large and com-
. A text-book of botany for secondary schools. Botany. 24 A TEXT-BOOK OP BOTANY with definitely spaced lines, preferably five millimeters apart.* As the leaf continues to grow, the most active growing, region will be indicated by the lines that draw farthest apart. 17. Protection.—Such an important organ as the leaf, with its delicate active cells necessarily in communication with the air, is exposed to numerous dangers. Conspicu- ous among these dangers are drought, intense light, and cold. Many ways of meeting these dangers have been developed by plants, but the subject is too large and com- plex to be presented with any completeness. The best that can Ije done is to select a few striking illustrations of protection that seem to be definite. Perhaps the most common danger to most plants is an excessive loss of water, and when a drought prevails the problem of checking trans- piration is a most serious one. As the leaves are the prominent transpiring organs, the chief methods of protec- tion concern A B Fig. is.—Sections through leaves of the same plant, showing the effect of exposure to light upon the structure of the nriesophyll: A, leaf exposed to intense sun- light ; B, leaf grown in the shade.—After Stahl. (1) The epidermis may be regarded as an ever-present check against transpiration (Fig. 12), for without it the * Such scales on stem and root are seen in Figs. 57 and 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 Merle, 1851-1928. New York, D. Appleton
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectbotany, bookyear1906
