eed OU RE 
409 
THURSDAY, AUGUST 31, 1899. 
PLANTS AND THEIR ENVIRONMENT. 
Les Végétaux et les Milieux Cosmigues (Adaptation— 
Evolution). Par J. Constantin. Pp. 292. Avec 171 
gravures dans le text. (Paris: Félix Alcan, 1898.) 
HIS little book has some admirable points which 
can be urged in its favour, and it also exhibits 
lacune which are a source of irritation to the reader. 
Chief amongst its more obvious defects is the entire lack 
of reference to literature. In a book of this sort such 
references are particularly desirable, as it will be read 
by many who may have no special first-hand acquaint- 
ance with the sources whence M. Constantin draws 
his facts. 
The book is well conceived and clearly written, though 
of course it makes no claims to be considered as an 
exhaustive treatise. 
The various kinds of surroundings in which different 
plants live, and the nature of the corresponding response 
on the part of the plant organism forms the main thesis 
of the book. An example will serve to illustrate the 
author’s method. 
The cold temperate climate on the whole tends to 
favour the production of dwarf plants, whereas the colder 
seas, as is well known, are the home of the largest alge. 
Ultimately both of these apparently contradictory effects 
are to be explained on nutritional grounds, the short 
period of terrestrial vegetation, during which alone 
assimilation can proceed, is to be contrasted with the 
more equable temperature of the sea, and especially 
with the fact that nutrition is favoured, in the case of 
aquatics, by lower temperatures, since gases are more 
soluble, and hence more abundantly at the disposal 
of the organism, than would be the case in warmer 
water. 
Similarly, the effects of light, gravity and aquatic sur- 
roundings upon the structure and form of plants are dis- 
cussed, and the reader will find much to interest him in 
the pages which deal with these topics. At the same 
time it must be confessed that the treatment strikes one 
as somewhat superficial at times, especially when the 
author wanders into the paths of theoretical inter- 
pretation. 
M. Constantin shares the belief, emphatically held by 
some German botanists, in the direct influence of the 
environment not only as modifying the form in the 
individual but also as impressing, without the aid of 
natural selection, that form on the species as part of its 
inherited stock ; and one chapter is devoted to an attempt 
to establish the thesis that acquired characters are 
inherited. As usual, however, in such cases, the mean- 
ing of ‘‘acquired characters” is not rigidly defined, 
nor separated from latent possibilities in the organism 
which the environment is able to emphasise simply 
by providing that stimulus which ensures their positive 
appearance. 
Some of these variations, responsive to the external 
requirements, are certainly very difficult of explanation 
on the doctrine of selection, but the opponents of this 
NO. 1557, VOL. 60] 
theory sometimes seem to overlook the fact that, in the 
first place, it is not in the least necessary to assume that 
| variations will be s/ég#¢,; they are often, on the contrary, 
in the case of specially plastic individuals, very extensive 
when these are subjected to a change of environment. 
And, in the second place, it is not necessary to suppose 
that any given species, and far less any individual, will 
vary equally in different directions round its average or 
mean. A very slight acquaintance with horticultural 
operations is enough to convince any one that certain 
races are specially plastic as regards one organ, whilst 
in others modification is most easily provoked in a differ- 
ent one. And selection, acting as it essentially does by 
eliminating those which conform less readily to the require- 
mentsof the environment, can hardly be dismissed, as M. 
Constantin dismisses it, as of relatively small importance 
in the evolution of species. But the difficulty really does 
exist if we only assume the possibility of slight variation 
ranged equally round a mean. In this case, of course, it 
is difficult (apart from isolation, physical or physiological) 
to see how a new species could be evolved at all when 
the chances of intercrossing are considered. But, as has 
been indicated, such a restriction is entirely gratuitous, 
and, furthermore, is contradicted by experience. 
The facts adduced by the author, drawn from the 
studies of Schiibeler and Bonnier, on the sudden 
evolution of spring- from autumn-wheat, hardly seem 
to help the case of the inheritable influence of the 
surroundings at all. For it is conceded that if autumn- 
wheat be sown in spring, a large percentage of the 
plants do not ripen fruit. Those that do succeed may, 
however, be supposed so to develop because their 
latent possibilities in this direction were greater than 
those possessed by their unsuccessful comrades. Next 
year, of course, the sowings obtained from the survivors 
will possess the same character for speedy growth and 
early maturity ina far larger average number, since the 
parents a@// had clearly a trend in the required direction. 
But it is misleading to speak of this as an inherited 
effect due to the impressed action of the environment, 
ze. the inheritance of an acquired character, for it is 
clearly nothing more than the encouragement of possi- 
bilities which were latent before, and, but for the changed 
conditions, might never have been raised to the position 
of criteria of existence at all, 
But this confusion between an outside moulding 
influence (e.g. mutilation) and the evoking from the 
plastic organism of a suitable response to the environ- 
ment imposed by new conditions, is very wide-spread ; 
and although the difference is in reality one altogether 
of kind, it is often in practice overlooked. 
A good summary is given of some of the interesting 
results obtained by French investigators on crossing 
races and species, but some of the other chapters strike 
one as rather weak, e.g. those dealing with the action of 
gravity on plants. The account of aquatic plants is also 
somewhat disappointing, especially as the author has 
himself worked in this branch of the subject. 
Nevertheless, the book is’ worth reading, bringing 
together as it does a considerable body of scattered 
facts which are lucidly arranged within a moderate 
number of pages. nets J. 
a 
