Lectures on the physiology of plants . one of themost general properties of vegetable organiza-tion ; indeed it is quite impossible for us tohave any idea of how plants would look, orcould exist, if their various organs were notanisotropous, and since their anisotropy is nothing other than the expression oftheir different irritability to the influence of gravitation and light, with which areassociated, in some cases, a sensitiveness for unequal distribution of moisture inthe environment, and probably some other less well-known influences, it is at onceobvious that it is the different irritabil
Lectures on the physiology of plants . one of themost general properties of vegetable organiza-tion ; indeed it is quite impossible for us tohave any idea of how plants would look, orcould exist, if their various organs were notanisotropous, and since their anisotropy is nothing other than the expression oftheir different irritability to the influence of gravitation and light, with which areassociated, in some cases, a sensitiveness for unequal distribution of moisture inthe environment, and probably some other less well-known influences, it is at onceobvious that it is the different irritability of the organs from which the externalconfiguration of plants in general arises—a statement from which I started in thelectures on Organography. Even the most important differences in the biologyof plants are the expression of the different distribution of anisotropy, of whichinnumerable examples may be quoted. To mention one only, the stem of Palmsgenerally grows vertically upwards, but there are also Palms [Sabal], the primary. FIG. 396.—Germinating-Water-nut (rra/ir natans]/coats of the fruit; w aborted root; h hypocotylc petiole of the large cotyledon which is buried in thseed ; c the small second cotyledon. Between thtwo cotyledons is the bud of the primary shoot. ANISOTROPY AS INFLUENCING TBE FORM OF PLANTS. 703 Stem of which, wilh its bud and the large foHage-leaves which it produces, bores downinto the earth, and since it cannot there advance, being a thick mass, it pushesthe old, properly lower, part of the stem upwards higher and higher above thesoil; similarly the great contrast between the common Ivy and its allies, themajority of the Araliacese, lies in their mutual difference in anisotropy: theshoot-axes of the Ivy climb, whereas the others erect their shoot-axes independentlywithout climbing. The Ivy teaches us, indeed, yet another important fact, viz. thatthe distribution of anisotropy in one and the same plant may alter at differentperiods of life. It is
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectplantph, bookyear1887
