SACS CONTAINING RESINS AND GUM-RESINS. 149 



a red-brown colour. The nature of the material composing this mass is not clear (comp. 

 Oudemans, /. c). According to the reaction with salts of Iron it contains much tannin : 

 it swells in water, alcohol, ether, glycerine, alkalies, acetic acid : it diminishes in volume 

 in mineral acids and salts of metals : the originally colourless mass is coloured by most 

 acids (also by iodine and sulphuric acid), alkalies, and metallic salts (with exception of 

 compounds of iron) a reddish brown, by Schultze's solution it is coloured blue. Carmine 

 and aniline colouring matters are taken up by it in very large quantity. 



Each of these peculiar structures originates, as Dippel has shown, from one simple 

 cell, which grows to a great length. The observation of their development in the 

 youngest internodes leads unmistakeably to this view. In the highest internodes of 

 Sambucus nigra tangential longitudinal sections, which include the peripheral zone of 

 pith uninjured, show cells with the above characters of the contents scattered in the 

 parenchyma: these are easily brought into prominence by their deep aniline-staining; 

 they are scattered through the parenchyma : the longest are almost of equal length to 

 the internode, the shortest are hardly twice as long as broad. In more elongated inter- 

 nodes, up to 5™™ long, the first sacs are already considerably lengthened, while new 

 cells, some placed alongside, some above the first, assume the same characters. Such 

 conditions at first sight allow of the assumption that the sacs arise from rows of coalescing 

 cells, but this is confirmed by no direct observation. In older and quite mature sacs 

 the mass of contents is easily divided, especially after the action of potash ', into cylin- 

 drical pieces sharply limited by transparent bands: these resemble cylindrical cells 

 arranged in longitudinal series : but from evidence derived from direct observation of 

 young stages of development they can only be regarded as products of the action of the 

 reagent. Drawings like Fig. 9 of Oudemans, /. c, represent doubtless something else 

 than the development of the sacs. 



4. The sacs containing gum-resin or latex which, according to Karsten, occur in all 

 species of the genera Cinchona and Xiadenbergia, appear to be closely allied to those 

 of Sambucus^. They are found, like these, partly in the periphery of the pith, partly in 

 the young outer cortex, close to the bast layer. In many species (C. heterophylla, 

 obtusifolia, &c.) they remain small, and are difficult to recognise even in the cortex 

 when two years old. But in other barks, such as those derived from Cinch, scrobiculata, 

 ovata, umbellulifera, &c., they attain a width of 100 ^i to over 300 /i, in C. lancifolia (?), 

 according to Vogl, even of 700^1, and a length of at least several millimetres. As far as 

 I could see they have conical closed ends : Karsten's statement that they arise from the 

 coalescence of longitudinal rows of cells certainly requires further investigation. The 

 sacs have a rather thick wall, which shows cellulose-colouring after treatment with potash. 

 Their contents, which include much tannin, are described as milky in the fresh state ; 

 in the dried bark they are so shrivelled that the sacs usually appear empty. 



5. A great number of CynareflB ', and many Vemoniaeeae, have in the stem, petiole, 

 and stronger ribs of the leaf on the outer side of the vascular bundles, or of the fibrous band 

 which limits them, a group of sacs filled with a fluid made milky by numerous resinous (?) 

 drops : this exudes on cut surfaces in the form of small white milky drops, and is thus 

 visible to the naked eye. In old sacs the contents coalesce to a very glutinous string. 

 In many species, e. g. Lappa, Cirsium lanceolatum, the sacs are placed not only at the 

 outer, but also at the inner margin of the vascular bundles. The sacs themselves have a 

 spindle-like form ; they are closed at both ends, and attain in the mature plant a con- 



' Compare Hanslein, I.e. p. 21. 



' Karsten, Die medic. China-Rinden Neu-Granadas, Ges. Beitr. p. 382.— Berg, China-Rinden 

 d. Pharm. Sammlg. zu Berlin.— Idem, Atl. d. Pharm. Waarenkiinde.— Vogl, China-Rinden d. Wiener 

 Grosshandels. — Fliickiger, Pharmacognosie, p. 566. 



' Trecul, Des vaisseaux propres . . . des Cynarees laiteuses . . . L'Institut, 1862, p. 266.— Vogl, 

 Ueber Milchsaftgefasse in der Klette; Botan. Zeitg., 1866, p. 193. 



