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HELIOTROPE, or TURNSOLE

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Originally appearing in Volume V13, Page 232 of the 1911 Encyclopedia Britannica.
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HELIOTROPE, or TURNSOLE, Heliotropium (Gr. fXtorpoiriov, i.e. a plant which follows the sun with its flowers or leaves, or, according to Theophrastus (Hiss. plant. vii. 15), which flowers at the summer solstice), a genus of usually more or less hairy herbs or undershrubs of the tribe Heliotropieae of the natural order Boraginaceae, having alternate, rarely almost opposite leaves; small white, lilac or blue flowers, in termitial or lateral one-sided simple or once or twice forked spikes, with a calyx of five deeply divided segments, a salver-shaped, hypogynous, 5-lobed corolla, and entire 4-celled ovary; fruit 2-to 4-sulcate or lobed, at length separable into four 1-seeded nutlets or into two hard 2-celled carpels. The genus contains 220 species indigenous in the temperate and warmer parts of both hemispheres. A few species are natives of Europe, as H. europaeum, which is also a naturalized species in the southern parts of North America. The common heliotrope of English hothouses, H. peruvianum, popularly known as " cherry-pie," is on account of the delicious odour of its flowers a great favourite with florists. It was introduced into Europe by the younger Jussieu, who sent seed of it from Peru to the royal garden at Paris. About the year 1757 it was grown in England by Philip Miller from seed obtained from St Germains. H. corymbosum (also a native of Peru), which was grown in Hammersmith nurseries as early as 1812, has larger but less fragant flowers than H. peruvianum. The species commonly grown in Russian gardens is H. suaveolens, which has white, highly fragrant flowers. Heliotropes may be propagated either from seed, or, as commonly, by means of cuttings of young growths taken an inch or two in length. Cuttings when sufficiently ripened, are struck in spring or during the summer months; when rooted I they should be potted singly into small pots, using as a compost fibry loam, sandy peat and well-decomposed stable manure from an old hotbed. The plants soon require to be shifted into a pot a size larger. To secure early-flowering plants, cuttings should be struck in August, potted off before winter sets in, and kept in a warm greenhouse. In the spring larger pots should be given, and the plants shortened back to make them bushy. They require frequent shiftings during the summer, to induce them to bloom freely. The heliotrope makes an elegant standard. The plants must in this case be allowed to send up a central shoot, and all the side growths must be pinched off until the necessary height is reached, when the shoot must be stopped and lateral growths will be produced to form the head. During winter they should A Qrom Jamin and Bouty, Ceurs de physique, Gauthier-Villars. rods EF, GF are such that BEFG is a rhombus. It is easy to show that rays falling op the mirror in the direction BC will be reflected along BD. One construction of the instrument, described in Jamin's Cows de physique, is shown in fig. 3. The mirror mm is attached Heliotropium suaveolens. be kept somewhat dry, and in spring the ball of soil should be reduced and the plants repotted, the shoots being slightly pruned, so as to maintain a symmetrical head. When they I are planted out against the walls and pillars of the greenhouse or conservatory an abundance of highly perfumed blossoms will be supplied all the year round. From the end of May till October heliotropes are excellent for massing in beds in the open air by themselves or with other plants. Many florists' varieties of the common heliotrope are known in cultivation. Pliny (Nat. hist. xxii. 29) distinguishes two kinds of " hello- , tropium," the tricoccum, and a. somewhat taller plant, the helioscopium; the former, it has been supposed, is Croton linctorium, and the latter the i?)uoTpolnov ,2tKp6v of Dioscorides or Heliotropium europaeum. The helioscopium, according to Pliny, was variously employed in medicine; thus the juice of the leaves with salt served for the removal of warts, whence the term herba verrucaria applied to the plant. What, from the perfume of its flowers, is sometimes called winter heliotrope, is the fragrant butterbur, or sweet-scented coltsfoot, Petasites (Tussilago) fragrans, a perennial Composite plant.
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