LATHR^A. 



[ 379 ] LATICIFEROUS TISSUE. 



&c. It appears to consist of a watery fluid, 

 with albumen in solution, in which float 

 globules of caoutchouc, or analogous gum- 

 resinous matter, of variable size, occasionally 

 mixed with starch-granules of peculiar forms, 

 as in Euphorbia (PI. 39. fig. 23). Schultz 

 attempted to show that there existed a regu- 

 lar circulation of the latex in plants, but the 

 idea is now abandoned by most observers. 

 See Laticiferous tissue. 



BiBL. Schultz, Sur la circulation et sur 

 les vaisseaux laticiferes dans les Plantes, 

 Paris, 1841; Von Mohl, Ueb. den Milchsaft, 

 &c., Botan. Zeit. 1843; Ann. Nat. Hist. xiii. 

 441. 



LATHR.EA. — AgenusofOrobanchaceous 

 Flowering Plants. L. squamaria, a remark- 

 able plant, found here and there in beech- 

 woods in England, has been tlie subject of 

 much research as regards embryology, by 

 Schacht and others. See Ovule. 



LATICIFEROUS TISSUE, ducts, 

 CANALS, or VESSELS. — Thcsc names are 

 applied to the tubular and often ramified 

 canals in which is contained the milky juice 

 or latex of many plants (figs. 392, 393). The 



Fig. 392. 



Fig. 393. 



Fig. 392. Laticiferous tissue extracted by maceration 

 from Leontodon Taraxacum. Magn. 100 

 diams. 



Fig. 39.3. Laticiferous tissue extracted from Chelido- 

 nium majus. Magn. 100 diams. 



nature, or rather the origin of these canals is 

 still a matter of dispute, the recent researches 

 of Schacht more particularly having dis- 

 turbed all the formerly received notions. 

 The ducts present themselves in various 

 forms and conditions, especially in the rind 



and pith in the Apocynaceai, Asclepiadacese, 

 Moracese, Urticaceae, Papaveraceae, Cucur- 

 bitaceae, Euphorbiacea?, Aroideae, &c. Sim- 

 ple unbranched milk- vessels occm* in the pith 

 of the elder. 



Schacht regards them all as liber-cells. 

 The opinion which we share \^ith almost all 

 other vegetable anatomists is, that they are 

 intercellular passages, originally devoid of a 

 proper coat, but subsequently acquiring one 

 of variable thickness, derived apparently 

 from the secretion which they contain. Un- 

 ger, however, imagines that while some are 

 formed in this way, they ai'e mostly deve- 

 loped out of confluent rows of cells, like the 

 dotted ducts. They requii-e much further 

 investigation. 



Canals bounded by a defined coat of cel- 

 lular tissue, forming intercellular canals or 

 ducts of very definite character, occur in the 

 Coniferae, the Guttiferse, Anacardiaceae, &c. 

 These will be spoken of under Recepta- 

 cles FOR SECRETIONS. 



Canals containing a milky juice occur in 

 some of the Fungi, as in the fleshy substance 

 of Agaricus deliciosus, quietus, and others 

 of the same section. 



It was declared some years ago by Schultz 

 that a regular circulation of the latex takes 

 place through the ramified laticiferous ducts. 

 This was chiefly supported on observations 

 of movements of the latex which may be 

 made on tolerably transparent parts of living 

 plants containing these ducts. By bringing 

 the uninjured sepal of Convolvulus or a leaf 

 of Chelidonium under the microscope (placing 

 it in oil is advantageous in the latter case), 

 the branched latex-ducts may be made out, 

 and a flowing movement of the particles may 

 be seen occasionally. But this has been 

 shown to depend upon a disturbance of the 

 equilibrium by external causes, such as pres- 

 sure and heat, and may be produced at will 

 in any direction by making an incision, to- 

 wards which the juice flows. 



BiBL. Schultz, Ueber Cy close derhebens- 

 saftes, Sfc, Nova Acta, xviii. pt. 2; Sur la 

 circulation, Sfc, Mem. des Sav. ^'c, Paris, 

 1841, Mohl, Vegetable Cell, p. 94. London, 

 1852, Ueber den Milchsaft, ^c, Bot. Zeit. 

 i. p. 553; Anonymous, Botan. Zeit. iv. p. 

 833 (1846) ; Schleiden, Principles of Botany 

 (London, 1849), p. 64 ; Unger, Grundzuge 

 der Anatomic und Physiologie (1846), p. 54 ; 

 Schacht, Botanisch. Zeit. ix. p. 513. 1851, 

 Die Pfianzenzelle, p. 210. Berlin, 1852; 

 Meyen, Secretions -Organe, p. 63. Berlin, 

 1837. 



