LETTTTCE. 163 LETJCKART. ers grow the seedling plants in the green- house or hot-bed and transplant 8-12 inches apart in the open field after the plants have been well hardened otT. The forcing of lettuce in green- houses has been an important industry in the vicinity of large cities in the Northern and Eastern United States. The other species of this genus exhibit nothing of the bland quality of the garden lettuce. The strong-scented lettuce (Lactuca virosa) is distinguished by the prickly keel of the leaves and by a black, smooth seed, with a rather broad margin. Lettuce Disea.ses. Lettuce, especially when forced or giown under glass, is liable to one or two serious fungous troubles. The most serious is known as 'rot' or 'drop,' which is due to at- tacks of Botrytis vulgaris. The presence of the fungus may be noted by a dark-colored decayed spot on the stem near the ground. Since the fungus is a soil growth, steaming the soil before planting in the benches is recommended. A tem- perature of 175 to 200 degrees is deemed sufficient if continued for an hour or more. Lettuce will grow at a temperature below that required for the development of the fimgus — a fact of which advantage may be taken. A mildew {Bremia hi-ctucw) attacks lettuce in the same condition as the rot. Care in ventilation will to a great degree control this disease. A rust due to Puccinia prenanthis and a leaf-spot caused by Heptoria consimilis sometimes attack lettuce, but aside from temporary disfigurement seldom occa- sion much loss. See Plate of Salad Plants. LETTUCE-BIRD. The American goldfinch (q.v.). LEXJBE, loiTje, Wiliielm (1842-). A Ger- man physician, specialist in diseases of the diges- tive organs. He was horn at L'lm, and studied at Tubingen, Zurich, Berlin, and Munich. In 1868 he became clinical assistant at Erlangen, and in 1885 professor at Wiirzburg. Leube specialized in physiological chemistry; with Rosenthal prepared a 'digested food' {Leubes Fleischsolution) ; and wrote: Veher die Wirkiong des Dihuidarmsaftes (1868); Ueber die ErnSh- riing vmn Mastdnrm o».«i (1872); Die Krank- heiten drf Miigeris iind Dnrms (2d ed. 1878) ; Bchnndlung dfr Uriimie (1883) ; Chemie in der Medizin (1884) ; and Spezielle Diagnose der hv- nern KranUheiten (1889-93). LEUCA'DIA. One of the Ionian Islands. See Santa Maura. LEUCHSENRING, loik'srn-ring. Franz Michael ( 1746-1827 ) . A German man of letters, born at Langenkandel in Alsace. Leuehsenring was a friend of Jacobi, Herder. Goethe, and Wie- land for a time, but they all broke with him. and Goethe portrayed him in no flattering colors in Pater Brey. He also describes him in Diehtung und Wahrheit. He was a sentimentalist, a mem- ber of the lUuminatrnarden, and continually sug- gested among his friends the foundation of a secret order of sentimentality. LEUCHTENBERG. loitt'ten-bgrK. See Beau- harnais. liETJCIN, lu'sin (from Gk. et/x6t, leukos, white; connected with Lat. lux, light, Olr. loche, lightning. OChurch Slav. Iiu'n, rav. Skt. rue, to shine, OHG. linht. Ger. Lirht. AS'. leoht, Eng. light). C,H„NO,. An amido-caproie acid whose chemical constitution is represented by the formula CH,.CH3CIi,CH,tH(XH,) .COOH. It may be obtained in the form of flat, glittering, white, odorless and tasteless crystals that are readily soluble in water and in alcohol, but prac- tically insoluble in ether. Neutral aqueous .solu- tions of leucin usually have the power of turn- ing the plane of polarized light to the left; the addition of acids or of alkalies, however, renders the solution dextro-rotatory. The leucin obtained from certain sources has no rotatory power at all. The importance of leucin in physiological chem- istry is very considerable. It is found normally in the liver, pancreas, spleen, thymus, thyroid and salivary glands, etc. In certain diseased conditions of the liver, leucin has been found in the urine. It is one of the characteristic prod- ucts of the pancreatic digestion of proteids, and it is formed wherever proteids undergo putre- faction and whenever they are decomposed by acids or alkalies. According to some authors, it is largely by the transformation of leucin that urea is formed in the animal body; this has not, however, been sufficiently proved and is rather improbable. Leucin may Iw conveniently pre- pared from horn-shavings by prolonged boiling vith moderately dilute sulphuric acid, neutral- izing with barium hydroxide, filtering, removing the excess of barium added with a little sul- phuric acid, again filtering, and evaporating the filtrate to a small volume; the leucin then crys- tallizes out together with some tyrosin, but as the latter is much less soluble than the former, it may be removed by several crystallizations from water. LEtJCIPI'TrS (Lat., from Gk. XdntTz-oc, Leuki/ipOfi I . The founder of the atomistic school of Greek philosophy, and forerunner of Deraocri- tus (q.v.). liETJCITE, lu'sit (from Gk. IcvkAc, leukos, white). An aluminum and potassium silicate that crystallizes in the isometric system. It is translucent to opaque, with a vitreous lustre and a smoky gray color. Leucite occurs chiefly in volcanic formations, and the best-known locali- ties are Vesuvius and Moiint Somma in Italy, where it is disseminated in grains through the lava ; also in the United States at various locali- ties in Wyoming. Millstones of this leucite lava have been found in the excavations at Pompeii. The white varieties, which resemble the common garnet, are called irhite garnet. LEUCKART, loi'kart, Rudolf (1822-98). A German zoologist, born in Helmstedt. He studied at Gottingen, and after teaching a few years there, he became, in 1850, professor of zoiilogy at Giessen, and at Leipzig in 1870. His early con- tributions to science attracted much attention. He divided Cuvier's type 'Radiata' into Echino- dermata and Coelenterata, and otherwise im- proved the system of classification. He also called attention to the division of labor in various colonial animals. During the latter half of his life he devoted himself almost exclusively to the .study of insects and parasitic worms, and became the greatest authority of his time on them. Of his numerous publications, the following are im- portant: Beitriige zur Kenntnis drr irirbrlloxen Thiere (with H.' Frey, 1847) ; Ueber Vorphologie and Verimndturhaft'sverhJiltnisse der tpirbellosen Thiere (1848): Veber Polymorphismus der In- dividuen oder die Erscheinungen der Arbeitsteil- ung in der Natur (1851) ; Veber die Uikropyle
