192 LATICIFEROUS TUBES. 



is very restricted, and not clearly proved hitherto by any observation. I was unable, 

 even in the milk-tubes, which are present in large quantities throughout the secondary 

 bast of jNIorus, Ficus, Madura, and Nerium, to prove that they arise successively 

 afresh from the cambium (Chap. XIV), and are not branches of the original tubes 

 which thrust themselves into the layers of secondary bast. A positive proof that the 

 latter is the case has, it is true, not been as yet obtained. 



The peculiarities of form and structure of milk-tubes in special cases of their 

 occurrence will, in order to avoid unnecessary repetition, be described together 

 wiih the treatment of their arrangement in Chap. XII. 



The peculiar juice which flows from milky plants, and the peculiar tubes which 

 contain it within the plant, were known to the fathers of vegetable anatomy, but with- 

 out their having sharply distinguished them from the reservoirs of resin and other se- 

 cretions, described in Sect. 34, and from the intercellular passages which so frequently 

 have contents of similar appearance. The terms then in use, viz.Succi proprii, and 

 reservoirs of such peculiar juices, referred rather to these latter forms of tissue and 

 cavities, or to their contents \ After many more or less successful attempts to distin- 

 guish them accurately and separate them (the history of which maybe found in Meyen 

 and Treviranus), C. H. Schultz-Schultzenstein from 1823 onwards^ drew the attention 

 of his contemporaries to the tubes with which we are engaged, and earned for himself 

 in his later works, especially two large publications in the year 1841 ^ the merit at least 

 of isolating by maceration the network of tubes of the Cichoracese, Campanulaceae, 

 and the tubes of the Euphorbias, &c., and drawing them for the most part correctly 

 in their main points. It is true his works were rendered unpalatable by his terrible 

 views on circulation, or, as he calls it, Cyclosis of the milk, or sap of life (Latex) in the 

 ' Vasa laticifera,' and that which was really good in his observations was hidden by 

 the mass of preposterous statements and representations into which he let himself 

 be led by the idea that networks of vessels of sap of life must be universally present. 

 Misunderstood sieve-tubes (the structure of these v/as quite unknown before 1837), 

 fungal hyphse (comp. Cyclosis, Taf. IV), and many objects which cannot be defined ac- 

 curately from the figures, were confounded with real milk-tubes Almost simultane- 

 ously with these larger publications of Schultz, and in connection with them, Meyen* 

 gave, on the whole, very good representations of the structure of a number of latex- 

 tubes, but without giving any close attention to the most elaborate networks of tubes 

 such as occur in the Cichoraceae and their allies. The knowledge of the structure 

 and distribution of the tubes was further advanced by Hanstein ^, Dippel ", and other 

 authors, to be named later, who have worked at their development ; Hartig"^ having 

 first sharply distinguished the articulated from the non-articulated forms, and Unger ^ 



' Compare Treviranus, Physiol. I. p. 137, &c. ; Meyen, N. Syst. d. Pflanzenphysiol. II. p. 371, &c. 



^ Ueber den Kreislauf des Saftes im Schollkraut. 



2 Die Cyclose des Lebenssaftes in den Pflanzen, Nov. Acta Acad. Leopoldino-Carolin, vol. 18, 

 Supplem. II. p. 336 S. 33 Taf. — Memoire pour servir de reponse aux questions de I'Acad. des Sci. 

 pour I'Annee 1833 ; Mem. pres. a I'Acad. des Sci. torn. VII. p. 104 S. 23 Taf. 



* Die Secretionsorgane der Pflanzen (1837), Physiol. II. pp. 376-3S6. 

 ^ Die Milchsaftgefasse, &c. Berlin, 1864. 



* Entstehung der Milchsaftgefasse, Verhandl. d. Bataafsch. Genootschap. &c. te Rotterdam, 

 torn. XII. p. 3 (1865). 



' Botan. Zeitg. 1862, p. 99. ' Anatomic und Physiologic, p. 157. 



