184 BOTANICAL GAZETTE [SEPTEMBER 
one and uneven texture makes it unfit for the more exacting 
uses to which maple wood is commonly put. 
The wood of A. saccharinum is shown in figs. 26, 27, 28, and 38. 
Here the tracheae are nearly circular in section, except where two 
or three are crowded together. The diameter is 20-40 pu, and the 
walls are o0.7-0.8 uw thick. In the older wood the tracheae often _ 
contain tannin plugs 250-300 uw in length. The oblique end walls 
have in most cases a tangential dip of 40-60°. The pit areas are 
hexagonal and 5-6 w in diameter. The transverse pits are about 
1uX2y. The thickenings in the walls of the smaller tracheae 
are sometimes scalariform, but not spiral. The tracheids are of 
two sorts, both rectangular in section in a large proportion of cases. 
(x) The summer tracheids are about 8-12 across, with walls 
1-1.5 thick, more highly lignified in the neighborhood of the 
tracheae. (2) The autumn tracheids appear as 1-3 rows of much 
flattened cells, 4-5 X10 4, with walls ‘1.5-2 thick. There is 
- often a very gradual transition from summer to autumn types of 
cells. The tracheids are 250-300 » long. Some wood parenchyma 
cells occur near the tracheae, but they do not contain either resin 
or crystals. 
The medullary rays are 1—3-seriate, 125-150 w apart, 200-500 
broad, and 20-30 u thick. The body cells are cylindrical, 6-10 » 
in diameter and 30-60 u long, with wallso.7 wu thick. The marginal 
cells are a little larger, triangular in section, and quite straight on the 
outer margin, as in the case of other true maples (figs. 35, 47); The 
pits are circular, large, and very numerous at points of contact 
with the tracheae. All ray cells contain much protoplasm and 
some starch. The end walls as seen in radial section are but 
slightly oblique, while in the transverse section they stand at an 
angle of 2o-30°. Large parenchymatous masses appear at intervals, 
connected with the medullary rays. 
In A. platanoides the tracheae are nearly round in transverse 
section, occurring in puonigs groups. The end walls have 4 
tangential dip of 30-40°. The smaller vessels show well marked 
spiral thickenings in their walls. The tracheids are of only one 
general sort, with a very gradual increase in thickness of walls and 
in lignification through the year’s growth. All are very irregular 
in shape. Some are considerably distended and show numerous 
