. Plants and their uses; an introduction to botany. Botany; Botany, Economic. EVOLUTION IN GENERAL 467 Many types of structure have become extinct, Ijecause changing conditions no longer afforded a suitable environ- ment, or, perhaps because no mutations of the old form could adapt it to new circumstances of peculiar difficulty. Relics of types which the world has thus outgrown have occasionally come down to us as fossils caught in the deposits which be- came rock in ages past. Sometimes a group, or perhaps part of its members, may have escaped extinction through the appearance of mutations. F
. Plants and their uses; an introduction to botany. Botany; Botany, Economic. EVOLUTION IN GENERAL 467 Many types of structure have become extinct, Ijecause changing conditions no longer afforded a suitable environ- ment, or, perhaps because no mutations of the old form could adapt it to new circumstances of peculiar difficulty. Relics of types which the world has thus outgrown have occasionally come down to us as fossils caught in the deposits which be- came rock in ages past. Sometimes a group, or perhaps part of its members, may have escaped extinction through the appearance of mutations. Fig. .304.—White Water Crowfoot {Ranunculus aqunlilis, var. capillaceus. Crowfoot Family, Ranunculacece). Plant, ai^out i. Flower. Fruit. (Britton and Brown.)—Perennial (?) herb about 30 cm. long; leaves submerged; flowers white; fruit dry. Native home, North America and Eurasia. fitting the individuals to live under less exacting conditions which therefore would permit simpler structure. Thus a buttercup able to live in water without being drowned could dispense with much of its root system and stiffening frame- work and ,so come to resemble, in the adaptation of its vege- tative organs to an aquatic life, a lower form of plant none of whose ancestors had been terrestrial. The white water crowfoot (Fig. 304) of our ponds and streams is a buttercup which we have every reason to believe has thus descended from a land species. In so far as a type of organism or organ. 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 Sargent, Frederick Leroy, 1863-. New York, H. Holt and Company
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbotany, bookyear1913
