257 
Groom.—Remarks on the Oecology of Coniferae. 
from Hough’s collection. To ensure uniformity of magnification, the 
vessels were drawn (with a camera lucida), and with the microscope im¬ 
movably fixed at a focus giving a magnification of twenty diameters. In 
order to ensure impartial observation the actual drawings were made by 
Miss Beatrice Rhodes. For the measurements I am responsible. The 
resultant figures as to the actual diameter of the vessels were obtained by 
calculating the mean of the two diameters of two tracheae of each species. 
In the subjoined tabular statement the statistics of the deciduous and 
evergreen species are given in parallel columns, viz. in the order of 
decreasing diameter of the tracheae. 
Deciduous Species. 
i. 
2 . 
5- 
6 . 
11. 
12. 
14. 
I 5 * 
Q. Michauxii 
Q. bicolor 
Q. alba . . 
Q. Muhlenbergi 
Q. aquatica . 
Q. palustris . 
Q. tinctoria . 
Q. coccinea . 
Q. rubra . . 
Q. Prinus 
Q. californica 
Q. Macdonaldi 
Q. macrocarpa 
Q. obtusiloba 
Q. lobata . . 
16. Q. Garryana 
Diameters of 
two tracheae 
magnified 
20/1 in mm. 
13 + 
J 3-5 + 
11 + 
10 + 
9*5 + 
9-5 + 
10 + 
10.5 
10 
10 
10 
7 
7 
9 
7 
7 
7 
7 
10 
10 
10 
9 
9 
I 8.5 
10 
9-25 + 
1 9 + 
( 9 + 
9 + 
8*5 + 
9*5 + 
8-5 + 
S 8-75 + 
{ 8-5 + 
9 + 
8 + 
9*5 + 
8-5 + 
9 + 
8 + 
■5 
■5 
■5 
■5 
■5 
5 
-5 
■5 
7-5 
7 
6.5 
7-5 
7*5 
8*5 
7 
5- 75 
6 
6 *75 
6- 25 
6.5 
6.25 
6 
5-75 
7 
5- 5 
6 - 5 
5-5 
5-5 
5 
5 
5 
Mean 
dia¬ 
meter 
in mm. 
0.587 
o-45 
°*45 
0.444 
0.438 
0-419 
0.412 
0.412 
0.387 
0.387 
0.378 
0.372 
0.372 
0-362 
o-356 
0 - 33 8 
Evergreen Species. 
Q. Engelr?ianni 
Q. agrifolia 
Q. virens . . 
Q. hypoleuca . 
Q. Emoryi. . 
Q. chrysolepis . 
Q. Wislizeni . 
Q. tomentella . 
Q. densiflora . 
Diameters of 
two tracheae 
magnified 
20/1 in mm. 
7*5 + 6 -5 
7 + 5-25 
7-25 + 5 
7.25 + 6.5 
7 +5-5 
7 +5 
7-25 + 5-5 
6*5 +4-75 
6-5 +5 
6-25 + 5-5 
6-5 +5 
6 +5-25 
6-5 +4-25 
6 +4 
5-5 +3-75 
5 +5 
5-5 +4-5 
4-5 +4-25 
Mean 
dia¬ 
meter 
in min. 
0.328 
o-325 
0.306 
0.300 
0-291 
0-284 / 
0.259 
Sub- 
ever- 
\ green 
for 
sub- 
deci¬ 
duous. 
0-241 
Truly 
1 ever- 
f green. 
0-234 
There are several points worthy of notice in connexion with these 
results :—• 
1. The sixteen species with the widest tracheae are deciduous. And 
the leading six of these include the only four species that habitually grow 
in swampy places. The last of the series, Q. Garryana , is described by 
S 
