Barber. — Cupressinoxylon vectense . 
345 
The Tracheides. 
The general arrangement of tracheides, as seen in transverse 
section, is fairly regular and similar to that in most woods 
of this class. Radial rows of broad cells alternate with narrow 
ones wedged in between them. The former represent the 
tracheides cut across at their broadest place, the latter 
the chisel-shaped ends with richly pitted walls. While the 
cells of each radial row are nearly constant in tangential 
width, neighbouring cell-rows differ very much. 
In order to measure the tangential width of the tracheides 
it is obviously impossible to isolate the cells and measure 
them individually at their broadest part, as has been done 
by Schulze for recent woods 1 . All that can be done is to 
obtain a general average of the tangential width by counting 
the number of cells in a measured distance 2 . This number 
will depend partly on the length of the tracheides ; the 
shorter these are, the more frequent will be the rows of 
narrow ends. 
It has been already pointed out that the cells vary in 
their size in wavy rings, being apparently much compressed 
where the arches join. It has therefore been found necessary 
to multiply observations in order to obtain a true average. 
The results appear to be in accordance with the general laws 
laid down by Mohl, Sanio, Schulze, Kraus, and Conwentz. 
The following figures give the measurements of from 100 to 
250 tracheides in each ring in eight different sections, the 
number of observations depending upon the state of pre- 
servation. They have involved the counting of over 
17,000 cells. 
1 Schulze, Ueber die Grossenverhaltnisse der Holzzellen bei Laub- u. Nadelholzern, 
Inaug. Diss., Halle, 1882. 
2 Sanio, Ueber die Grosse der Holzzellen bei d. gemein. Kiefer, Pringsh. Jahrb. 
viii, 1892, p. 403. 
