Text-book of structural and physiological botany . mber of leaves is due to a colouring matter contained intheir cells, chlorophyll (see p. 24). In some etiolated [sapro-phytic or parasitic] plants, as Oroba?iche, it is wanting; inothers the leaves are variegated or coloured white, red, oryellow, in patches. The colour of the leaves of many plantschanges more or less in the course of the year. Thus theleaves of the grape-vine, which are at first green, often turn red in the autumn ; v/hilethose of the copper-beechare reddest in the spring,and afterwards becomemore and more green. SUBSIDIARY OR
Text-book of structural and physiological botany . mber of leaves is due to a colouring matter contained intheir cells, chlorophyll (see p. 24). In some etiolated [sapro-phytic or parasitic] plants, as Oroba?iche, it is wanting; inothers the leaves are variegated or coloured white, red, oryellow, in patches. The colour of the leaves of many plantschanges more or less in the course of the year. Thus theleaves of the grape-vine, which are at first green, often turn red in the autumn ; v/hilethose of the copper-beechare reddest in the spring,and afterwards becomemore and more green. SUBSIDIARY ORGANS. Under this head areincluded a number of struc-tures which maybe regardedas appendages to the or-gans already are in some casesmodified parts of thestem or leaf, in others aspecial development of theepidermis which forms theouter covering of them are tendrilsor ci7^rhi, filiform struc-tures which cling roundneighbouring substances, and whose function is to enableweak plants to attach themselves to, and to climb up. Fig. 196.—Stem-tendrils of the grape-vine ;V in the normal state ; v bearing a bunchof grapes. The External Form of Plants, 109 stronger plants. Accordingly as they belong to the stem as inthe vine (Fig. 196), or to the leaf as in the tare, they arecalled stem- or leaf-tendrils. The same distinction is madebetween branch-spines as in the sloe (Fig. 197), and leaf-spi7ies as in the holly (Fig. 172, p. 98); , stiff and verysharp-pointed structures arising from the transformation of astem or leaf, or a part of one of these organs, and which aretherefore not mere epidermal growths. ^ Prickles, although
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