120 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
fruit. These are fairly uniform and constant, but when we 
come to dead matter, such as a plank or log of wood, or a piece 
of furniture, we have not these appearances to guide us, and in 
the manufactured article staining and colouring, in imitation of 
choice and valuable woods, oblige us to appeal to the microscope, 
which shows us a constant uniformity in the appearance of the 
tissue of any piece of timber of whatever species. To illustrate 
this, we may take Plates 56 to 64, on which the different appear- 
ances, in section, of different woods can be compared. By 
comparing the transverse section of Quercus Robur on Plate 57, 
with the section of Scots Fir on Plate 61, the difference is 
clearly observed. Then take the transverse section of Cupressus 
Lawsoniana on Plate 58, and compare it with the sections of 
Pines on Plates 61 and 64, the great difference will be readily 
observed, there being no resinous canals in the Cypress. Again, 
taking the section of Alnus glutinosa on Plate 62, and comparing 
it with Ulmus campestris on Plate 63, an outstanding difference 
will be at once noticed. So uniform and constant are the 
appearances in the various genera that produce timber, that it 
is almost impossible for the student of forestry to make a 
mistake in identifying any piece of timber he may be required 
to examine. But when we come to examine the different species 
of the same family or genus, there is also found to be a consider- 
able relative difference. For example, Plate 43, Quercus Suber, 
compared with Plate 10, Quercus Ilex, shows much difference, The 
reasons for such differences are still involved in obscurity. This 
diversity is nct so apparent in the roots of trees; in fact, one might 
say there is an entire absence of difference, the roots of the various 
species of the same family constantly presenting the same appear- 
ance. In general appearance the roots of Exogens are usually the 
same as the stem. They have no pith, however, leaf-buds, nor 
stomata, but they possess all the other characteristics of the stem. 
The roots of the different trees may be easily distinguished one from 
another by the vascular tissue and medullary rays. Examples 
of this are given on Plates 65 to 73; while Plates 74 (the root 
of a Fern) and 99 (the root of the Common Dock) show a contrast 
in structure. It will be observed that the roots of the Beech, 
the Cedar, the Whin, and the Oak show, in the transverse 
section, all the characteristics of the stem. But while the roots 
have usually no normal leaf-buds, yet adventitious buds spring 
from the spiral tissue of the medullary rays. 
