OF THE WOOD OF INDIAN SPECIES OF PINUS. 459 
and often exceed these dimensions. The species whose spring-tracheids come 
next in width are likewise pines growing often in subtropical or even tropical 
climates, namely P. longifolia (555 wand 39:5 ш), and P. Khasya (52 u and 
25 ш), which grows in places among tropical plants in Burma. The temperate 
P. excelsa and the xerophilous P. Gerardiana have much narrower spring- 
tracheids, the respective diameters being 38°5 w and 37:5 p in the former, 
and 34 u and 29 u in the latter. 
These distinctions suggested to one of us an enquiry into the effect of 
environment and systematic affinity on the width of  spring-tracheids 
of species of Pinus. A separate paper * deals with this, but the main results 
are given here, 
Pinus Gerardiana has the narrowest spring-tracheids either because it is 
xerophilous or because it belongs to the sub-section Para-Cembra, group 
* Parrya." Тһе observed mean diameter of its spring-tracheids was 
31°5 u—those of the tour haploxylie American species T with the narrowest 
spring-tracheids varied from 24 to 33 p. 
Pinus eæcelsa has broader. spring-tracheids, either because it is not 
xerophilous or because it belongs to the section * Cembra” and group 
Strobus. The observed mean diameter of the spring-tracheids was 38 д. 
Those of the American specics belonging to the same group varied from 
41°5 to 45 р. 
Pinus longifolia, P. Khasya, and P. Merkusit have widest tracheids 
because they are sub-tropical or tropical in distribution with sufficiency of 
moisture. 
In the case of the rather xerophilous P. longifolia, as in those of American 
species of sub-tropical distribution in a moist climate, the periodically or 
permanent dry nature of the superficial soil is not associated with narrowness 
of spring-tracheids. The mean diameter of its spring-tracheids (4675 и) 
may be compared with those of two sub-tropical American species, P. clausa 
(A8 д) and P. palustris (49 ш), growing on dry sand in a moist climate. 
The sub-tropical and perhaps tropical P. Ahasya, in which the observed mean 
diameter of the spring-tracheids was 4375, practically agrees with the sub- 
tropical and tropical P. cubensis (44 ш) that grows in South Carolina and 
the West Indies. 
Finally, the most tropical Asiatic species P. Merkusii has the widest 
spring-traeheids (565 ш), just as is the case with the most tropical American 
‘species P. tropicalis (50°8 ш). 
* Percy Groom, “ An Enquiry into the Significance of Tracheid-width in Conifer,” ined. 
+ In comparing the figures with those given by Penhallow for American species, it must 
be pointed out that we measured the widest of the spring-tracheids, but we do not know 
whether Penhallow followed the same procedure’ or took the mean diameter of ail the 
-spring-tracheids. 
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