340 MANIPULATION. 



nified at D ; in this are exhibited the zones, a a, indicating the 

 annual growth of the stem and the radiating hnes, b b, termed 

 the medullary rays. A vertical section, B, through the pith, 

 win exhibit the meduUary rays ; these are known to the cabinet- 

 maker as the silver grain, and at E, which is a magnified 

 view of a part of the same, may be seen the woody fibres, c c, 

 with their dots, d d, and the horizontal Hues indicating the 

 medullary rays cut lengthwise; whilst at C, which is the 

 tangental section, and F a portion of the same magnified, the 

 openings of the medullary rays, ff, and the woody fibres with 

 vertical slices of the dots, are exhibited. Very instructive 

 preparations may be made by cutting oblique sections of the 

 stem, especially when large vessels are present, as then the 

 internal structure of the walls of some of them may often- 

 times be examined. The diagram above given refers only to 

 sections of a pine ; all exogenous stems, however, will exhibit 

 three different appearances, according to the direction in 

 which the cut is made, but in order to arrive at a true 

 understanding of the arrangement of the woody and vascular 

 bundles in endogens, horizontal and vertical sections only will 

 be required. Many specimens of wood that are very hard 

 and brittle may be much softened by boiling in water, and as 

 the cutting-machine will answer for other structures besides 

 wood, it may here be stated, that all horny tissues may also 

 be considerably softened by boiling, and can then be cut 

 very easily. 



Method of Mounting Sections of Wood. — The thinnest and 

 most perfect sections having been selected, they may be 

 mounted either in fluid, in Canada balsam, or dry, the 

 former plan being by far the best, especially for the vertical 

 and tangental sections ; the transverse, when mounted either 

 in balsam or dry, do not lose so many of their striking 

 characters as the others, and this is the more to be remarked 

 when the wood has been kept for some considerable time 

 previously in a dry state. Vegetable sections will keep very 

 well in almost aU the preservative solutions; on the whole, 

 perhaps, the weak spirit and water and the gelatinous medium, 

 page 312, will be the best; they may be mounted either in 



