51 
1?AMABACK, Larix Americana, Rlichx, No. 401. 
The photomicrograph of the transverse section shows a zone of hard, 
dense, nearly solid tracheids, which form from one-sixth to one third of 
the annual ring, and, like those of Pinus palustrtSj have a sharp line of 
demarcation where the two classes join in the ring. These two species 
of trees attain their greatest development in opposite portions of the 
country : the Tamarack in the North, and the Yellow Pine in the 
South. The resin-canals in the former are confined to the zone of 
thick-walled tracheids, and are usually near the outer portion of the 
ring. The cells which form the exterior portion of the canal are much 
thicker and firmer than those in Pinus palustris, and the area of the 
canal is also much less. Generally two canals are in close proximity, 
but without any apparent connection. 
The thin-walled tracheids in different trees vary somewhat in size, 
ranging from 0.0025 of an inch to 0.002 of an inch in diameter in a ra. 
dial direction, and from 0.002 to 0.0015 of an inch in a longitudinal 
direction. The lumen measures from 0.001 of an inch to 0.0013 of an 
inch, the walls being much thicker than those of some other woods, 
a feature which gives this wood greater wearing qualities. 
In many parts of the transverse section the division between the la- 
mella* joining the cells can be seen, something that cannot be made out 
in any of the other Conifers. The medullary rays are quite numerous 
and of considerable size, showing their cavity quite clearly with this 
magnifying power. The lenticular markings on the cells are most 
abundant near the ends, and less frequent in the middle, and the swell- 
ing of many of the walls parallel to the medullary rays is due to the 
cross-section of such markings. This peculiarity of the markings is 
also seen in the radial section. 
In the radial section the lines crossing the page represent the medul- 
lary rays, the walls of which are very thick and strong, the thin places 
in them being very small. M the central ray is seen a longitudinal sec- 
tion of one of the resin-canals of the medullary system. In the tangen- 
tial section the medullary rays are seen to be cells arranged in single 
rows, usually from six to eighteen cells superimposed one above the 
other, except in those rays inclosing a resin-canal. The thickness of 
the wails is very apparent, and of great importance in preventing decay. 
The quality of the wood of this tree is such that it deserves to be 
more widely known and more extensively used for ties than it has been ,* 
yet where its growth is abundant adjacent to their lines, a few railroad 
companies have employed it for ties. But it was only in a few locali- 
ties, where the timber was thus situated, that these ties were found 
recently put in. Each annual ring has a zone of hard, dense tracheids, 
which render it capable of sustaining the heaviest freight traffic; its 
durability, too, is another feature of great importance. 
Preservation and Fungi. — This wood is easily treated with antiseptics 
to prevent decay, especially with sulphate or acetate of iron - 7 and ties 
