OF THE WOOD OF INDIAN SPECIES OF PINUS. 169 
the hypoderma. All these facts collectively seem to indicate that these three 
species of Pinus live in a region of considerable annual rainfall, but can 
endure a considerable season of drought. 
As regards features of systematic significance, P. Merkusit is perhaps the 
most interesting abietineous plant in existence from the point of view of 
structure of wood, which shows possible relations to the araucarian type of 
pitting on the radial walls. So far it is the only existing conifer known to 
have these pits arranged in the cluster-like manner already described. In 
certain Cordaites (C. Newherryi) the pits are arranged in clusters which in 
the successive tracheids of a radial row form a radial series, so as to present 
the appearance of the possibility that the grouped pits correspond to the 
position of contiguous medullary rays. The pits forming one group or cluster 
are more numerous than in Pines Merkusit. Gothan (1910) describes and 
figures a fossil conifer, Cedroaylon transiens (Gothan), whose wood shows in 
some of the tracheids typical araucarian pitting, and in other tracheids little 
clusters of 3—4 pits, very similar to those of P. Merkusii, He regards this 
clustered arrangement as the first step in the change from an araucarian type 
of pitting towards the abietinean condition. If this “star-like” (as Gothan 
terms it) arrangement is thus a transitional stage between the two conditions, 
P. Merkusti completes the picture by providing a type that has the typical 
abietinean pitting and the clustered * star-like " arrangement, so that the 
stages between the two extremes are now known. P. Merkus also shows 
appearances that may be interpreted as transition between the alternate 
(araucarian) and opposite (abietinean) arrangement of these pits (fig. 46). 
So far as we are aware no other living conifer, outside the Araucariacez, has 
triseriate pits In. the ‘adial walls of the spring-tracheids : the pits are not 
arranged alternately as in the araucarian type, hut are opposite. 
SPECIAL DESCRIPTION OF THE SPECIES. 
PINUS GERARDIANA (Wall). 
Pinus Gerardiana, the Himalayan edible pine, a species with its leaves in 
3-needled tufts, is clearly xerophilous in distribution, as it occurs in the 
“inner dry and arid West Himalaya” (Gamble, 1902), at altitudes varying 
from 5,000—10,000 ft., also in Afghanistan, Kafiristan, and in the Hariab 
district (7,000—11,000 ft.), moreover the species is social on * dry steep rocky 
slopes" (Gamble). The thick leaf is xerophytie in structure, for the epidermis 
has very thick walls, including thick cuticle and cuticular layers ; the stomata 
are sunk, and there іх a thick-walled hypoderma. Despite this xerophilous 
distribution and xerophytie structure the bark is “ very thin, grey, smooth, 
and cracked only in very old trees " (Gamble). Europe, however, supplies 
an analogue in Betula alba, whose habitat is often dry. 
