TOBACCO, the name gis.t-n to the leaves of several species of ifieutiosso pre• parrd in varfoul ways mainly for smoking or tbewing purposes, and in the powdered for inhalation snuff The use of obacco 14 more widely spread than k that any other narroet or ‘timulant, Botany.—Few of the numerous species of Nicotiana possess any economic importance. The great bulk of the world's tobacco supply is derived from N. tabacum, the Virginian tobacco, a plant indigenous to America. It is a coarse rank-growing annual, with a simple, un branched, cylindrical stem, which often ex ceeds 6 ft. in height The stem terminates in a panicle of pink or rose-coloured flow ers, possessing an elongated corolla tube (fig. I). The plant has alternate, simple, oblong-lanceolate leaves, those at the low er part of the stem being slightly stalked, and of large size, reaching to 2 ft. in length, while the upper leaves are semi amplexicaul and of variable outline. The seeds are brown in colour, with a rough surface, and are so small and numerous that i,000,000 may be produced by a single plant. The stem and leaves of the plant are covered with long soft hairs which exude a viscid juice, giving the surface a moist glutinous feeling.
From this species, N. tabacum, the tobaccos of Cuba, the United States, the Philippines, Canada, Nyasaland, Rhodesia and the Latakia of Turkey are derived, and it is also largely grown in India : the variety macrophylla is the source of Maryland to baccos. N. Persica, regarded as another American variety of this genus, yields the famous Shiraz tobacco of Persia. N. rustica is a smaller branching plant with greenish-yellow flowers, and although a native of Mexico it is much cultivated in the East Indies.
Given suitable climatic conditions, the type of tobacco produced is determined mainly by the character of the soil, which should be well drained, and contain a large percentage of humus. Clay
soils, retentive of moisture, as a rule yield heavy-cropping to baccos which cure to a dark brown or red colour, while sandy soils produce tobaccos with a thin leaf, curing to a yellow or bright reddish colour. Cultural details necessarily differ accord ing to the locality, and the type of labour employed, but those prevailing in the United States, the chief source of tobacco, may be taken as fairly representative, and are hereafter described.
The seed is sown in nursery beds and the plants set out in the field later. Great care is taken in the preparation of the seed-bed, which should lie in a sunny situation, protected from winds, and be composed of good, rich soil in fine tilth. When necessary, hot beds are used. Insect pests are destroyed by burning fires, raised by intervening logs above the surface of the ground, or by steam ing the bed. Fertilizers, usually guano or chemical manures, are incorporated with the surface soil, which is pulverized to 3 in. in depth. The seed, owing to its minute size, is usually mixed before sowing with a relatively large quantity of fine ashes, sand or meal, to ensure even distribution. Deep burying of the seed must be avoided, and the young and delicate seedlings carefully watered and if necessary shaded, during the early stages of growth. With seed of good quality a half-ounce of seed is sufficient for a bed of about 6o sq.yd., and will yield about 40,000 plants for transplanting.
The well hardened seedlings are transplanted into rows from 3 to 4 ft. apart, with a distance of from i 2 ft. to 3 ft. between the plants, cigar types being the closer-spaced varieties. When the flowering buds appear, these are removed by "topping," and also the suckers which are subsequently produced. A limited number of leaves only is allowed to develop, ranging from 8 to 12 in the heavy types and from is to zo or more in cigar wrapper and binder varieties, Burley and Maryland. Cultivation under artificial shade has been found beneficial in some districts and this method is used with great success in the Connecticut valley and Florida for cigar wrapper leaf.