Groom.—Remarks on the Oecology of Coniferae. 263 
Jiiiiiperus recurva , occurring at an altitude of 16,000 feet on the Himalayas, 
yet thrives in Calcutta Botanic Gardens (but without flowering in the latter 
place, as Colonel Prain informs me). The Scots pine occurs in extremely 
varied habitats, as is notorious. 
The genus Pinus shows a climatic range of distribution that I believe 
to be unequalled by any dicotylous arboreous genus. Occurring in arctic 
regions (at 70" N.), it extends southwards to the Equator (in Sumatra); 
and in southern Burma has one species, P. Merkusii> occupying a truly 
tropical position at only 500 feet above sea-level. Pinus includes species 
growing beyond the altitudinal and latitudinal limit of forest. Some species 
live in good soils in company with dicotylous trees and demand moist air ; 
others occur in Mediterranean and Californian regions among sclerophyllous 
vegetation, often on particularly dry sites ; still others grow in dry sterile 
sands or in swamps of various types (peat-bogs, wet sand, muddy swamp). 
The mechanism that permits of such range of single species or genera 
must be an efficient one under very diverse circumstances, and must afford 
ample explanation of the survival of modern Coniferae. Certainly the 
plasticity of the coniferous evergreen foliage of one species is usually under¬ 
estimated, first because its most obvious feature concerns differences in the 
length of the needles (which differences may exceed 1,000 per cent.), but 
the needles also show change of thickness and surface, and above all they 
exhibit great differences as regards longevity, so that the Scots pine, for 
instance, may prolong the life of some of its needles from the average 
2-3 years to 8-9 years. The general impression that the evergreen north- 
temperate Conifer as a working machine is inferior to that of the deciduous 
dicotylous tree in the same region is, perhaps, a mistaken one. The two 
types of trees may represent rather two alternative mechanisms of approxi¬ 
mately even efficiency when in normal action ; and the low-tension coniferous 
machine in places outworks its high-tension tropophytic rival. 
(/) The Vulnerability and Suppression of Coniferae. 
If then the coniferous mechanism in normal working really be as 
efficient as the dicotylous mechanism, it would seem possible that the 
defeat of the Coniferae by dicotylous trees and the suppression of many 
forms are due to the coniferous machine being more easily put out of order 
or being more exposed to injury. 
In connexion with the second alternative, there is no doubt that the 
tree preserving its xerophytic leaves during the physiologically dry season, 
or in extremest conditions, is exposed to greater danger of desiccation than 
is a tree that is devoid of foliage during the same season. Though, as Von 
Hohnel points out, we cannot rely upon his results as regards the amount 
of water given off by trees during winter (as the trees were kept under 
shelter in a room), the results sufficiently indicate the greater loss of water 
