. The essentials of botany. Botany. PLANT PHTSIOL007. 107 movements, which are all referable to the activities of pro- toplasm, may he grouped under the following heads, viz.: Nutation (or Automatism), Geotropism, Heliotropism and Irritability. 183. Nutation.—Under this term are gathei-ed those cases in which terminal parts of plants move spontaneously and somewhat regularly in definite directions. It has been observed that the grow- ing ends of climbing plants perform circular nutations; thus in the hop and honey- suckle the free ends of the stems rotate in the direction of the hands of a wat
. The essentials of botany. Botany. PLANT PHTSIOL007. 107 movements, which are all referable to the activities of pro- toplasm, may he grouped under the following heads, viz.: Nutation (or Automatism), Geotropism, Heliotropism and Irritability. 183. Nutation.—Under this term are gathei-ed those cases in which terminal parts of plants move spontaneously and somewhat regularly in definite directions. It has been observed that the grow- ing ends of climbing plants perform circular nutations; thus in the hop and honey- suckle the free ends of the stems rotate in the direction of the hands of a watch (Fig. 56«), while in the yam, bean, and morning-glory the rota- tion is the reverse (Fig. 565). In other cases the nutation is a simple swaying back and forth, as in many leaves and growing shoots. 184. Mr. Darwin has shown that as soon as a seed ger- minates the little root at once begins a sort of revolving motion, its tip describing more or less elliptical or circular figures. By this circumnutation a root is enabled to find those places in the soil which offer the least resistance to its passage. Moreover, it has been shown that the tip of the root is sensitive to pressure, and when it comes in contact with any object bends from it. In this way the root-tip guides the advancing root through the interstices of the soil, avoiding on every hand the pebbles and harder bits of earth. The root-tip appears also to be sensitive to. _ Twining stems—o, of hop; b, of 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 Bessey, Charles E. (Charles Edwin), 1845-1915. New York : Holt
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectbotany, bookyear1896
