SANTALACH^. 237 



of tliem reminding one extremely of tlie fibres, of which the 

 pinewood is made up. I have also noticed intermediate 

 fibres, marked with both true annular and laterally extended 

 pits (IToftiipfel and Spalttiipfel). The vessels are short, 

 somewhat obliquely truncated, and perforated with a great 

 annular hole, the ends of the vessels being more or less 

 pointed. 



" Only the heartwood is valuable, the sapwood and branches 

 being not used. I failed, in fact, in demonstrating the 

 presence of oil in the sapwood, the tissue of which is nearly 

 colourless, and exhibits no contents at all in its cells. In the 

 heartwood, on the contrary, the cell- walls are very rich in yel- 

 low colouring matter. The parenchymatous part of the wood^ 

 the medullary rays and numerous vessels are loaded with a 

 yellow-brownish resinous matter. Thin slices, examined under 

 water or glycerine, display a great many smaller and larger 

 drops, soluble in alcohol and reducing osmic acid (1 part dis- 

 solved in 100 parts of water) ; no doubt they are drops of essential 

 oil. These drops, flowing out of the ducts, on thin sections are 

 seen most abounding along the primary membranes of the cells 

 and in their pits. But if rather thick sections are treated with 

 osmic acid, the woody parenchyme and the medullary rays also 

 assume a black colour, due to reduced osmium. If, on the con- 

 trary, the sections, before being treated with osmic acid, have 

 been well washed with alcohol, the just mentioned parenchyme 

 is not at all or but extremely faintly blackened. The cells 

 under notice contain no tannic matter, as shown by means of 

 bichromate of potassium and chloride of iron, the reduction of 

 the osmic acid is consequently not due to tannic matter. Small 

 pieces of the heartwood were further treated for some days with 

 a solution of osmic acid, then extracted by means of alcohol and 

 dx'ied. When sections were made from these pieces, I ascertained 

 that nearly all the parenchymatous parts had assumed a black 

 colour. Sometimes also the libriform cells contain a small 

 amount of oil, but the experiments just mentioned prove the 

 parenchymatoiis tissue of the wood to he the principal scat of the 

 essential oil. When treated with a mixture of equal parts of 



