VI COLOURS OF PLANTS 407 
long summer days. “The farther we advance towards the 
north the more the leaves of plants increase in size, as if to 
absorb a greater proportion of the solar rays. M. Grisebach 
says that during a journey in Norway he observed that the 
majority of deciduous trees had already, at the 60th degree 
of latitude, larger leaves than in Germany, while M. Ch. 
Martins has made a similar observation as regards the legu- 
minous plants cultivated in Lapland.”! The same writer goes 
on to say that all the seeds of cultivated plants acquire a 
deeper colour the farther north they are grown, white hari- 
cots becoming brown or black, and white wheat becoming 
brown, while the green colour of all vegetation becomes more 
intense. The flowers also are similarly changed : those which 
are white or yellow in central Europe becoming red or orange 
in Norway. This is what occurs in the Alpine flora, and the 
cause is said to be the same in both—the greater intensity of 
the sunlight. In the one the light is more persistent, in the 
other more intense because it traverses a thinner atmosphere. 
Admitting the facts as above stated to be in themselves 
correct, they do not by any means establish the theory 
founded on them; and it is curious that Grisebach, who has 
been quoted by this writer for the fact of the increased size 
of the foliage, gives a totally different explanation of the 
more vivid colours of arctic flowers. He says: “ We see 
flowers become larger and more richly coloured in proportion 
as, by the increasing length of winter, insects become rarer, 
and their co-operation in the act of fecundation is exposed to 
more uncertain chances” (Vegetation du Globe, vol. i. p. 61— 
French translation). This is the theory here adopted to 
explain the colours of Alpine plants, and we believe there are 
many facts that will show it to be the preferable one. The 
statement that the white and yellow flowers of temperate 
Europe become red or golden in the arctic regions must, we 
think, be incorrect. By roughly tabulating the colours of 
the plants given by Sir Joseph Hooker? as permanently 
arctic, we find among fifty species with more or less con- 
spicuous flowers, twenty-five white, twelve yellow, eight 
1 Revue des Deux Mondes, 1877—" La Vegetation dans les hautes Lati- 
tudes,” par M. Tisserand. 
2 Qn the Distribution of Arctic Plants,” Linn. Trans. vol. xxiii, (1862). 
