94 VIEWS OF THE MICROSCOPIC WOKLD. 



greatly magnified. The strong lines a a a a a a a, are the rays of cellular tissue 

 which proceed from the centre to the bark, but on account of the smallness 

 of the sections magnified, their divergence from each other is too small to be 

 detected. The remaining portions of the wood consist of a perfect chainwork 

 of cells, formed of the cellular tissue. These cells are compressed, like those of 

 the Oak, at regular intervals, as shown at 6 b b b b 6, in directions apparently at 

 right angles to the radial insertions. The width of the cells, where they 'are 

 not compressed, is about the twelve hundred and fiftieth part of an inch, and 

 the thickness of one of the radial insertions, as a b b 6, is a little less than the 

 nineteen-hundredth part of an inch. 



WHITEWOOD. The elegant structure of a transverse section of Whitewood, as 

 revealed by the microscope, is displayed in figure 142. The four heavy lines, 



Fip. 142. 



running in a parallel direction with each other, are some of the radial in- 

 sertions of cellular tissue, and in thickness do not exceed one-twelve hun- 

 dredth part of an inch. 



The large openings scattered throughout the wood are sections of the spiral 

 vessels, the diameters of which, when largest, measure only the three hundredth 

 part of an inch. The rest of the space is filled with a most exquisite network 

 of fibres, the meshes of which are angular in form, the whole surpassing in 

 the delicacy of its texture, the fabric of the finest laces. 



SUMACH. A singular figure is exhibited in drawing 143, which represents one 

 eighth part of a cross section of the common Sumach of one year's growth. 

 The bark occupies the space A B K L, the pith that of E F G, while the 

 wood, including the sap-wood K L C D, is comprised within the limits K L E F. 

 The bark is covered with a down of fine hairs, which when magnified, fringe the 

 section with the thorn-like figures a a, as shown in the drawing. Most ot 



