52 
so treated have lasted over thirty years under heavy traffic. These ties 
were originally 9 feet long, having been moved under the rails three 
times, and were destroyed only by continued spiking. The sap-wood 
did not show evidence of decay exceeding one-eighth of an inch in 
depth ; while the wood within was sound and bright. Untreated Tama- 
rack ties last from five to eight years. 
The decay was not uniform 5 in most cases it was from the outside in- 
ward, the sap-wood being destroyed first; in others the decay was from 
the bottom upward. Unfortunately, however, these observations are 
somewhat incomplete, as the history of the ties could not be satisfac- 
torily traced. 
The fungi which grow on this wood are Polyporus pinicola, Fr., and 
Polyporus dbietinus, Fr. 
Western Larch, Larix occidentalism Nuttall. Xo. 402. 
The photomicrograph of the transverse section shows this to be a 
much harder and more dense wood than that of the preceding species ; 
the thin tracheitis are larger and nearly rectangular, the largest of them 
measuring .0025 of an inch, with a lumen .002 x .002 of an inch, the 
walls of which are comparatively thick. 
The decidedly tabular thick-walled tracheitis measure .002 x .0013 of 
an inch, the lumen being very small, in many cases only a trace of a 
cavity $ and, comparatively speaking, the thick-walled cells comprise a 
greater number of rows than the thin-walled ones, a feature which gives 
to this wood increased hardness, strength, and elasticity over the pre- 
ceding species. The line of demarcation between the two classes of 
tracheitis in the same layer is distinct and sharp. 
The number and form of the resin -canals is quite similar to those of 
the common Tamarack. In the radial section the lenticular markings 
are not so frequent ; generally but one row is found on the side of the 
thin-walled tracheitis, where, in the preceding species, there are com- 
monly two rows. The medullary rays are in broati bantis, with a struct- 
ure almost identical with that of the Tamarack. In the tangential sec- 
tion the medullary rays are in single rows, except when inclosing a 
resin-canal; but the cells are larger and more conspicuous than in the 
preceding species. 
Table I. — Comparative average number of fibers in a square of wood Too of an inch on a 
side, or — otttt of the area of a square inch. 
No. 
Woods. 
Remarks. 
251 
290 
329 
380 
387 
401 
402 
White Oak 
268 small fi bers in the dense masses. 
150 " " " " " Great variation in 
different specimens of tins wood. 
110 thick tracheids ; 70 thin tracheids. 
60 thick tracheids ; 30 tbin tracheids. 
80 thick tracheids ; 38 thin tracheids. 
116 thick tracheids ; 33 thin tracheids, 
54 thick tracheids; 24 thin tracheids. 
White Cedar..... 
Hemlock 
Tamarack 
'1 
