LATICIFEROUS TUBES, DEVELOPMENT. 193 



having given a short and clear, though not quite correct review of the leading types. 

 A great service in advancing the knowledge of these organs was further rendered by 

 Trecul, who, in a series of papers published since 1862, described his very numerous 

 observations, and thereby gave the impulse to the new works on the development of 

 these organs. It is true TrecuP inclines again to the old idea of circulation, and places 

 the milk-tubes nearer other reservoirs of ' sues propres ' than is allowable from an 

 anatomical point of view. 



Finally, Vogl- has supplied a number of valuable contributions and confirmatory 

 observations. 



The history of the origin of the milk-tubes, so indispensable to a clear under- 

 standing of their structure, remained long in the dark^. Unger's view *, according to 

 which (from observations on Ficus benghalensis) they arise from rows of cylindrical 

 cells by coalescence, found no response, and opinions remained undefined, till in 

 1846 the often-mentioned anonymous writer in the Botanische Zeitung expressed 

 the opinion, as the result of an extended series of investigations, that each milk-tube is 

 originally an intercellular passage without a wall of its own, which is subsequently 

 provided with a membrane peculiar to it, through the agency of the adjoining cells. 

 The contradiction by Schacht^ of this view, which was at first not unfavourably 

 received, and the subsequent answer by Trecul, called forth the series of newer 

 works, by which the anonymous writer was refuted, and a clearer knowledge of the 

 matter was gained, at least in many particulars. Unger formulated his view afresh in 

 1855*, in these words. The milk-tubes are 'shorter or longer, cylindrical, irregular 

 or branched cells, filled with opaque milky or dark coloured juice, which fuse 

 with one another in longitudinal rows or at their points of branching.' He lays 



* From the series of Trecul's papers which treated of ' sues propres,' those 011 milk-tubes may 

 here be named : Des vaisseaux propres en general et de ceux des Cynarees laiteuses en particulier, 

 L'Institut, 1862, p. 266. — De la presence du latex dans les vaisseaux spiraux . . . . et de la circulation 

 dans les plaiites, Comptes Rendus, torn. 45, p. 402 (1857). — Des laliciferes dans les Papaveracees, 

 Ibid. torn. 60, p. 522 (1865). — Sur les laticiferes des Euphorbes, &c., Ibid. tom. 60, p. 1349. — Lati- 

 ciferes et liber des Apocynees et des Asclepiadees, &c., Ibid. tom. 61, p. 1349 ; L'Institut, 1862. p. 215. 

 — Des laliciferes dans les Chicoracees, Ibid. tom. 61, p. 785 (1865). — Des laticiferes dans les Cam- 

 panulacees, Ibid. p. 929. — Des vaisseaux propres dans les Aroidees, Ibid. tom. 6i, p. 1163 (1865), 

 et tom. 62, p. 29 (1866). — Matiere amylacee .... dans les vaisseaux du_latex de plusieurs Apocj'nees, 

 Ibid. tom. 61, p. 156 (1865). — Rapport des laticiferes avec le systeme fibro-vasculaire, Ibid. tom. 5:, 

 p. 871 (i860). — Rapports des vaisseaux du latex avec le systeme fibro-vasculaire; ouvertures entre 

 les laticiferes et les fibres ligneuses ou les vaisseaux; Ibid. tom. 60, p. 78 (1865). — Des vaisseaux 

 propres et du tannin dans les Musacees, Ibid. tom. 66, p. 462 (1868). — Most of these works were 

 reprinted in the Annales des Sciences Naturelles ; all in Baillon's Adansonia, tom. VII-IX. 



^ Ueber die InterccUularsubstanz und die Milchsaftgefasse in der Wurzel des gemeinen Lovven- 

 zahns, Sitzungsbr. d. Wiener Acad. Bd. 48. — Beitrage z. Kenntniss der Milchsaftorgane d. Pfl., 

 Pringsheim's Jahrb. V. 



^ [On this subject see further Schmalhausen, Beitr. z. Kenntniss d. Milchsaftbehiilter d. Pflanzen, 

 Mem. de I'Acad. Imp. de St. Pelersbourg, XXIV. 1877.— Faivre, Compt. rend. hebd. t. LXXXVIII. — 

 D. H. Scott, Development of articulated laticiferous vessels. Quart. Joum. Micr. Sci. 1882. — E. 

 Schmidt, Botan. Zeitg. 1882, p. 435. — Treub, Comptes rend. 1 .Sept. 1879, Archives Neerlandaises, 

 t. XV]. 



* Annalen des Wiener Museums f. Naturgesch. bd. II (1840), p. 11, where it is attempted to 

 adduce a proof, weak enough even for that time. — Endlicher u. Unger, Grundziige (1843), p. 40. 



^ Botan. Zeitg. 1851, p. 513. "^ Anatomic und Physiologic, p. 157, 



O 



