SECONDARY THICKENING. NORMAL DICOTYLEDONS. 509 



means to be asserted that in the woods in question they alone saturate the heart- 

 wood, and may not perhaps be mixed with other bodies which have not been 

 minutely investigated, or that differences may not prevail between the mixtures 

 which occur in the membranes and those in the cavities. On these questions no 

 sufBciently accurate investigations exist. In a number of Dicotyledonous woods, 

 which do not serve as dye-woods (Ailantus, Prunus domestica, spinosa, Amygdalus 

 communis, Zanthoxylon fraxineum, Rhamnus cathartica, Sorbus Aucuparia, Gle- 

 ditschia, Periploca, &c.), bodies were found by Sanio ^ both in the interior of the 

 vessels and in the membranes, which on their first appearance in the interior of 

 the vessels were colourless, but afterwards came to differ from one another in their 

 yellow or red colour, while they agreed together in their high resistance to all 

 solvent agents. Caustic potash does not change them; Schulze's mixture at boiling- 

 point first produces discolouration, and then solution. 



It is thus quite possible that the appearance of a definite body, or of a series 

 of substances, which are nearly related, and vary in the different kinds of wood, 

 may be generally characteristic of the process of metacrasis which produces the 

 duramen, and that the appearance of resins, of special colouring matters, and 

 so on, may only be a phenomenon peculiar to particular cases, and accompanying 

 the former changes. 



In Caragana arborescens Sanio found that only air is at first contained in the 

 vessels of the yellow heart-wood; at a somewhat later stage he found a yellow 

 body with the properties above-stated ; in the discoloured central portion, which is 

 limited by a red ring, and even in the red ring itself this body had again disappeared. 

 This phenomenon can afford no argument against the view that the appearance 

 of the infiltrating substances in question is characteristic of the formation of dura- 

 men, but can only indicate that in certain cases they may undergo displacement, 

 or further processes of rapid decomposition. 



Inside the vessels and cell-lumina the infiltrating bodies of whatever kind 

 appear at first in the form of deposits on the wall, often in two layers ; here and 

 there, where they are accumulated in large quantities, they show hemispherical 

 prominences, projecting inwards, or sometimes form biconcave plates extending 

 transversely through the lumen; the masses are homogeneous, rarely granular 

 (Castanea vesca), frequently with flaws and cracks. All these phenomena point to 

 the fact that they first appear in the fluid form, and afterwards harden. Very 

 extensive accumulations fill the lumina completely, as for example in the Guaiacum 

 and Ebony woods. In the vessels and crevices of the Campeche wood, greenish 

 crystals (Hsematoxylin ?) sometimes occur '■'. 



It is remote from the purpose of this book to discuss the question, so difficult in 

 the defective state of chemical knowledge on these subjects, as to the origin 

 of the infiltrating substances, and more especially to investigate how far they are 

 derived from the transformation of other pre-existing substances, at the same 

 places in which they occur, to what extent they have been conveyed to these 

 places from elsewhere, and in the latter cases what their origin is. Attention may 



' Botan. Zeitg. 1863, p. 126. — Compare also Hartig, ibid. 1859, P- i°0' 

 ' FlUckiger and Hanbury, Pharmacographia, p. 188. 



