LATEX 337 



of their contents. These laticiferous elements are long, and as a rule 

 abundantly branched tubes, which traverse the roots, stems and leaves 

 in all directions ; they are accordingly well fitted for transporting 

 materials on a considerable scale. 



The walls of latex-tubes are soft, and as a rule also thin, except in 

 the genus Euphorbia, where they attain a thickness of from Ol-'OIG 

 cm., being at the same time unusually extensible and elastic. Pits are 

 scantily developed even in the more thick-walled types. In Euphorbia 

 Lathyris the author has noticed that exceedingly narrow pits sometimes 

 occur where the wall of a latex-tube abuts against palisade-cells, while 

 the regions of the wall bordering upon spongy parenchyma bear larger 

 pits, with their closing-membranes perforated by very conspicuous pro- 

 toplasmic threads. Kienitz-Gerloff has similarly demonstrated the 

 existence of protoplasmic connections between laticiferous tubes and 

 adjacent parenchymatous cells in Euphorbia Cyparissias and in Nerium. 



From the researches of Treub and Emil Schmidt it appears, that 

 even fully-developed latex-tubes contain a peripheral layer of protoplasm, 

 in which large numbers of nuclei may be suspended. Various circum- 

 stances, such as the production of adventitious branches and the 

 occlusion of severed latex-tubes by means of a callus-like formation (in 

 the root of Scorzonera and the stem of Euphorbia splendens), lead one to 

 conclude that the protoplasts in these structures retain their vitality for 

 a long time. 



Latex, the characteristic substance contained in latex-tubes, is usually 

 a milk-white, more rarely a pale yellow (Argemone) or even orange- 

 coloured (Chelidonium), liquid. Ontogenetically considered, it corre- 

 sponds to the cell-sap, at any rate according to Schmidt, Kallen and 

 Molisch ; Berthold, however, considers that it represents a peculiarly 

 modified liquid protoplast. Latex always takes the form of an emulsion 

 composed of innumerable minute granules and drops, suspended in a 

 watery liquor which contains other substances in solution. The 

 suspended particles are of very diverse kinds, and comprise granules of 

 resin, gum or caoutchouc which tend to form coherent masses when 

 the latex exudes oil-drops, tannin vesicles, protein crystalloids and 

 (in the Euphorbiaceae) small starch-grains. These starch-grains are 

 remarkable for their peculiar shapes ; in our native Euphorbias they 

 are generally spindle-shaped, while in the tropical species they are 

 flattened with expanded ends, thus resembling miniature thigh-bones or 

 dumb-bells. Potter states that they are formed in connection with 

 amyloplasts, just like ordinary starch-grains. Molisch has recorded the 

 occurrence of large numbers of protein-granules, which are likewise 

 formed by special plastids, in the latex of Cecropia pcltata and Brosimum 

 macrocarpum. The watery matrix of the latex may contain a variety 



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