LEADING OF VOICES. 44 LEAF. fourtli), wluToas the latter adiiiit^i suoli intervals uiuUr iiMtain circiiinstaiioi's. Ajjain. there is greater freedom in the jiroj^ression of voices in instrumental eomposilinns than in voeal. because pure intonation of dillicntt intervals is more eas- ily attained by means of an instrument than by the human voice. In the leadinjr of voices it is also of great importance whether a voici' or part is real or only rcvnforcing. LEADING TONE OB NOTE. In music, the major seventh of the dialoiiic scale, or the semi- tone below the octave, to which it leads. The resolution of this note in a cliord is always a scmistep above. Hence it can never be doubled, as open octaves would result in the progression to the next chord. See Harmony. LEAD-POISONING. See Lead. LEADS, Ti!E (Tt. / Piombi). The prison cells inider the leaden roof of the Doges' Palace at Venice. They were destroyed in 1707. LEAD'VILLE. A city and the county-seat of Lake County. Colo., 78 miles in a direct line southwest of Denver: on the Colorado .Midland, the Denver and Rio (irandc. and other railroads (Map: Colorado, D 2). The surrounding scenery ofTers magnificent attractions; an<l the city itself, at an elevation of 10,200 feet, affords much of unusual and striking interest. There are large sampling, refining, and reduction works, and smelting furnaces; also a handsome theatre, the Tabor Opera House ; hospitals ; and a United States fish-hatchery. Leadville was incorporated as a town in 1877, and as a cilv in 1878. Popu- lation, in 1800, 10,.384: in lOOo! 12.455. Settled in 18(i0, Leadville soon becam<< promi- nent as the centre of an active gold-mining in- dustry. The apparent exhaustion of the gold deposits during the following decades, however, gave a serious set-back to its progress, and it did not regain its importance until 1870. after large bodies of lead-silver ores had been opened in California Gulch, from half a mile to four miles distant. The population increased from about 300 in 1877 to at least liOOn in the following year and to 15.000 in 1870. Olher rich silver de- posits were soon found on Carbonate. Iron, and Fryer hills in the Mosquito range, and the min- eral output for Ix'adville during the period 1870-02 reached the tot.-il of .$170,000,000. Fur- ther prospecting has since been rewarded by the discovery of rich ores within the city itself, thus assuring a long life to its mining industry. For some time the region about Leadville held first place in the production of lead and silver, and it is now gaining a prominent position as a producer also of gold, zinc, copper, bismuth, and manganese ores. LEAF (AS. leaf, Goth. Inufs, OHG. Joub. Ger. Laub. leaf). A lateral usually green outgrowth from the stem of a plant, whose principal func- tion is to elaborate food. The most conspicuous form is the foliage leaf: that is, one which con- tains gieen tissue and is prominently concerned in food manufacture, (See Piiotcsynthesis.) Very simple expansions of green tissue, which are commonly called leaves, occur among the algae, especially the more complex 7iiarine forms, and in the case of the leafy liverworts and the mosses. But the highly organized foliage leaf is found only in the fern-plants (pteridophytes) and seed-plants ( spermatophy tes ) , associated with the vascular system. Such a leaf may develop several distinct regions, the most conspicuous of which is the expanded portion or blade. In many cases where the blade arises directly from the a.is, and no other region appears, the leaf is called sessile. Very frequently, however, the blade has a stalk of greater or less length, called (he petiole. In many cases, also, the petiole bears at or near its junction with the axis a pair (if appendages of various form, called stipules. The stipules may be cons))icuous and leaf-like m merely minute bract-like bodies; they may In- distinct from one another or united in various ways. In the smartweeds they unite and form a conspicuous sheath about the stem just above the insertion of each leaf. Still another leaf region which may appear conspicuously in grasses is the sheath, which more or less surrounds the stem. The angle formed by the petiole with the stem is called the axil. Forms of Leaves. The form of the blade varies greatly, and has given rise to a long list of descriptive terms, which are of .service only to the specialist in classification. These terms apply to the general outline of the leaf, as linear, lanceolate, ovate, cordate, etc.; or to the char- acter of its margin, as entire, serrate, toothed, lobed, etc; or to the character of its apex or base, as acute, obtuse, etc. The greatest modi- fication in the form of the blade arises from its branching, in which case the general blade be- comes divided up into snuiller blades called leaf- lets. Such branching leaves are usually called compound, and the compounding may occur twice or thrice or even more times, resulting in a gen- eral blade made up of very numerous leaflets. Fig. 1. TYPES OF venation. 1, parallel : 2, pinnate; 3, dichotomons. The stalks of the leaflets are called petiolules, and their stipules are stipels. Closely associated with the contour and branching of leaves is the sys- tem of veining or venation (q.v.). Tw-o general types of venation are recognized, called the parallel and the reticulate (or net-veined) types. In .1 parallel-veined leaf the prominent veins run approximately parallel from the base to the apex of the blade, resulting in a comparatively nar- row and elongated outline and an entire margin, as in grass-blades. This type of venation is characteristic of the monocotyledons, although all of them do not possess it, nor is it absolutely restricted to them. A more significant phrase for
