DE CANDOLLE ON SPECIES. 
191 
of the full grown cup is fairly constant, but the form of the base often 
varies, as from turbinate to hemispherical and from blunt to atte¬ 
nuated;—the gibbosity of the bases of the scales varies very much, 
their direction, which is always straight when young, becomes patent 
or reflexed in age, but mature normal cups are very constant in this 
respect;—terminations of the scales of the cup, in some species the 
upper scales of the cup elongate into a recurved narrow lamina; this 
character is not always constant, and Michaux asserts, that in dense 
forests after a hot summer, the scales do not elongate at all;— 
Acorn, its length varies much in relation to the cup, or rather, there 
are different epochs of maturation, at which acorns of different dimen¬ 
sions are produced; thus the Spaniards say that Q. Buber yields 3 
crops, and the acorns of each have a different name. Be this as it may, 
nothing is more common than to find on the same branch acorns in¬ 
cluded and exserted from their cups. 
Again, M. De Candolle finds that certain characters vary accord¬ 
ing to the age of the plant; thus the leaves of young shoots of oaks 
are usually sharper at the base, less cut or toothed, and shorter 
petioled than those of old shoots, besides being of a very different 
form. Lastly, the duration of the leaves of one tree sometimes varies 
from year to year, according to the season. 
The characters which M. De Candolle has never found to vary 
on the same branch , are, the size, pubescence, and to a great extent the 
form of the stipules; the direction, size, and to a certain degree the 
number of nerves of the leaf; the pubescence of the leaves and 
branches, the hairs being isolated or fascicled, their presence on the 
nerves and parenchyma, and their length on the young organs; the 
duration of the foliage ; glabrous or pubescent anthers ; the form of 
the upper part of the ripe normal cup ; size of the cup ; general form 
and relative size of the scales of the cup ; annual and biennial matu¬ 
ration of fruit; position of atrophied ovules in the ripe acorn. 
The above observations are probably the most accurate and 
important of their kind that have ever been brought together, and 
for them the thanks of Naturalists are pre-eminently due.- TJpon 
Palaeontologists, especially, their study should be urgently enforced, 
for the very characters here authoritatively shown to be most variable 
on single branches , are most frequently the only ones of which the 
Palaeontologist can take cognizance ; wdiereas of all those pronounced 
constant, that of the nervation is the only one of which they can avail 
themselves ; and it is to be borne in mind, that M. De Candolle only 
answers for the invariability of these last, on the same branch. Of 
course exceptions may be taken to any one of these results, and no 
other accumulation of specimen s would give precisely equivalent ones 
to those M. De Candolle has obtained ; but of their general accuracy 
we have as little doubt as there can be of the author’s scrupulous care 
in observing and recording them. 
Then follows a discussion upon the principles which M. De Can¬ 
dolle has attempted to follow in determining what to regard as species 
