SECTIONS OF WOODS GROWN IN BRITAIN. 43 
In the Maples (Figs. 8 and 9) the medullary rays run straight 
out from the pith, and are very numerous. The vasa are uniformly 
distributed in groups of from two to five, and are nearly of the 
same size, giving the wood of the whole tribe that even consistency 
which makes their timber of so great value for certain purposes. 
The vasa in the wood of the Poplars (Fig. 14) and the Willows 
(Fig. 19) are extremely numerous, nearly of equal size in the 
spring and autumn growths, and regularly distributed throughout 
the wood. The medullary rays are also numerous, straight, and 
very small in all the species. 
In the Beech (Fig. 11) the medullary rays are large and numerous, 
the vasa being pretty uniformly distributed throughout the tissue. 
It is the oak tribe, however, which shows itself the most distinct. 
In it the vasa are very numerous, and of various sizes in the same 
group, gradually diminising in size as the season’s growth advances. 
These vasa or cells are surrounded by organised tissue. The latter 
is connected to the spiral filament contained in the cell, which in 
turn is connected with the medullary system. This, however, is 
true of several other genera of timber trees. The medullary rays 
in the whole of the oak tribe are very large, but comparatively few 
in number. 
Botanists have classified, in a general way, the vasa or pores, 
and the medullary rays, into six sizes. The vasa are arranged thus— 
those of the category of the Oak, large; Common Elm, mediwm 
large ; Whin, mediwm ; Maple, fine ; Spindle Tree, very fine ; and 
Holly, extremely fine. The medullary rays are classified in the 
same manner, viz.—those of the size of the Oak, very large; 
Alder, large; Sycamore, medium large; Common Maple, medium ; 
Ash, narrow ; and Birch, very narrow. 
If these woods are examined through an ordinary pocket-lens, 
this typical arrangement will be found to be pretty nearly 
correct. It will be found absolutely correct, if due allowance 
is made for age, and for the position in which the timber has 
been grown. For example, if the vasa and medullary rays of a 
stunted Oak are compared with those of a vigorous Spanish 
Chestnut, the vasa of the latter will be found slightly larger, but 
there is quite an outstanding distinction in the surrounding tissue, 
as well as in the medullary rays, pointing clearly to the fact that 
the wood is not oak, 
From the illustrations, it will be observed that some hardwoods 
resemble each other in their general features. For example, the 
