1884. 87 Trans. N. Y. Ac. Sci. 
Greenland, and thence migrate to low latitudes without change of 
character, if—to say nothing of temperature—the manner of supplying 
solar influences was then as different in the two regions as it 
now is. 
It certainly was to be expected, if plants are to be affected by their 
surroundings, that natives of high latitudes, adapted to continuous 
months of sunlight and of darkness, would fail to endure the altered 
conditions, or else would exhibit indications of changes in structure 
to correspond to the altered requirements. 
This belief is strengthened by the fact that ‘‘in receding from polar 
toward equatorial latitudes, the Alpine or mountain floras really 
become less and less Arctic.” * The only changed conditions in such 
cases are those due to the difference in the length of days and nights. 
Another corroboration is afforded by the peculiar structure of a 
conifer found standing in lat. 724$°,+ and microscopically examined by 
Sir WILLIAM HOOKER. It differed remarkably from all other conifers 
known to him. Each annual ring consisted of two zones of tissue ; 
the inner, narrow, of a dark color, and formed of slender woody fibres 
with few or no discs upon them; the outer, broader, of a pale color, 
and consisting of ordinary tubes of wood fibre marked with discs, such as 
are common to all conifere, These characters were found in all parts 
of the wood. They suggest, he says, the annual recurrence of some 
special cause which modified the first and last made fibres of each 
year’s deposit ; and this cause he thinks is found in the peculiarity of 
an Arctic climate, where the days were at first very short—a few hours 
only of sunshine. Then the first and imperfectly developed fibres 
were formed. As the days grew longer, the solar rays at last became 
continuous, the woody fibres became more perfect, and were studded 
with discs of a more highly organized structure than are usual in the 
natural order to which this tree belongs. 
The absence of such structure in Spitzbergen, 5° further north, if 
established, would strengthen the conviction that such days did not 
occur there in the much earlier times, to which its trees belong. 
Since Arctic climate, in those early periods, was warm through the 
year, it follows that—with the earth’s axis inclined 23}°—the plants 
of Spitzbergen and other equally high latitudes must have spent four 
months of each year in darkness, and surrounded by a moist and 
warm atmosphere. Modern vegetation, so placed, bleaches and dies ; 
could the result then have been different, if the axis was inclined as 
now ? 
Undoubtedly, a flora might have been specially organized for such 
* Quoted approvingly by Mr. Darwin, in Origin of Species, from Mr. H. C. Watson. 
+ See account in Climate and Time, pages 264 and 26s. 
