] -O SECRETORy RESERVOIRS. 



."^iderable lenglh, exceeding 3 — 4"""; they have a moderately thick membrane wliich 

 shows no important peculiarity. 



The above sacs may occur in certain species of a genus, and be absent in others. Trecul 

 found them in Cirsium arvense, oleraceum, lanceolatum, anglicum, palustre, prsealtum: 

 Carduus nutans, crispus, tenuifiorus, Onopordon acanthium : Carlina vulgaris, longifolia, 

 salicifolia: Jurinea alata, Notobasis syriaca, Tyrimnus leucographus, Galactites tomen- 

 tosa, Duria;i, Silybum marianum, Echenais nutans, Arctium lanuginosum ; Lappa com- 

 munis: — Vernonia emincns, noveboracensis, pra-alta: — but they are absent, according to 

 the same author, in Vernonia flexuosa Sims., and in the Cynareae of the genera Cynara, 

 Rhaponticum, Acroptilon, Serratula, Carduncellus, Centaurea. 



6. The secretory sacs of the species of Acer', which are usually called laticiferous 

 vessels from their milky contents, are of cylindrical prismatic form (on the average 

 about I"'™ long and 50-60 /ii broad in A. platanoides), and are arranged in rows longitu- 

 dinally one upon another. Their colourless cellulose walls are as a rule completely 

 closed, the terminal surfaces, which fit one on another, are horizontal or oblique, the lateral 

 surfaces often have short sac-like protrusions, and with these pit-like thinner-walled pro- 

 trusions they press sometimes between the limiting surfaces of neighbouring parenchy- 

 matous cells, sometimes on the lateral walls of other similar sacs. In surface view these 

 thinner-walled protrusions appear as broad, round or transversely elliptical, clearly 

 marked pits, which are smooth, not latticed. I never saw any perforation of the ends. 

 The open lateral communications described by Hanstein, between neighbouring sacs, by 

 means of perforated lateral protrusions, I was al-,o unable to find in sections which had 

 not been macerated : but they were often found just as represented by Hanstein (/.c. 

 Fig. 6) in macerated preparations, even if these (from A. platanoides) had been prepared 

 only by boiling in water. The contents of two sacs, coagulated by boiling into masses, 

 then hung together by a short bridge, which loosely filled a corresponding canal. How 

 far these conditions exist in the living plant, or have arisen as products of maceration, 

 i.e. by rupture of a closed lateral protrusion due to boiling, I must leave undecided. 



The sacs are solitary or in groups of 2-4, surrounded by parenchyma: they lie on the 

 limit between the phloem of the vascular bundle and the bundle of sclerenchymatous 

 fibres, which surrounds this externally, at that point in fact where in other plants the 

 first-formed sieve-tubes stand (comp. Chap. VIII) : they are also found in the primary 

 bark of branches, and in the petiole and ribs of the leaf. They do not extend further into 

 the parenchyma of the leaf, nor are new ones formed in the secondary bast. Among 

 the species investigated, they are largest and most numerous in A. platanoides. They 

 are developed very early in the internodes, and seem to have special significance during 

 their early stages ; still, according to Hartig, they remain filled with sap in the 

 branches of A. platanoides for about ten years. In A. saccharinuni and monspessulanum 

 their sap appears, according to Hartig, not to be milky. 



7. The peculiar resins of the Convolvulaeese ^ occur in sacs, sometimes as nearly 

 homogeneous masses, but more frequently forming with watery solutions milky mix- 

 tures: these sacs have usually been called 'laticiferous vessels' from the latter peculiarity 

 of their contents. 



The sacs have been observed in all investigated herbaceous species : they are found, 

 according to the species, in stem, roots, ribs of leaves, or only in certain of these parts : 

 they occur especially in the parenchymatous cortex, and in the bast of the stem and 

 roots: they are ranged one above another in rows, which run longitudinally through the 

 members, and are isolated, or numbers are grouped together: the latter is the case, 



' Hartig, Naturgesch. d. forstl. Culturpflanzen, p. 545. — Botan. Zeitg. 1 862. p. 98. — Hanstein, /.c. 



- Trecul, Des Laticiferes des Convolvulacees ; Comptes Rendus, torn. LX. (1865), P- 825. — 

 A. ^'ogl, Ueber Convolvulus arvensis ; Schriften d. Wiener Zool. Bot. Gesellsch. 1863, p. 258. — 

 Idem, Zur KennUi. d. Mikhsaftorgane d. Pfl. ; Pringsheim's Jahrb. bd. V. p 31. 



