DAUBENY ON THE INFLUENCE OF CLIMATE. 
509 
between dicotyledons and monocotyledons, it is true, are usually very 
marked ; but these differences are by no means of either the kind or 
extent Dr. Daubeny here endeavours to make out. The excuse may 
be offered that his explanation was not intended for a scientific, but for 
a general audience. But this will scarcely serve to palliate the gross 
inaccuracy of his statements, which run thus:—“ Dicotyledonous 
plants, such as those which constitute the forests of this and other 
moderately warm climates, consist of a series of concentric layers of 
wood and bark, between each of which we may suppose a stratum of 
confined air to be interposed.” And, “ monocotyledonous trees, of 
which palms afford us the most familiar examples, consist merely of 
one hard concentric layer of ligneous matter, inclosing a soft pulpy 
substance, full of juice.” Dr. Daubeny says it cannot “ be wondered 
at that they (Dicotyledons) should be tolerant of cold, both when 
we consider the slowly conducting power of dry wood of all de¬ 
scriptions, and also that of the air detained within the interstices of 
the timber itself.” Were the structure of these two grand types 
what they are here represented, we might indeed be willing to grant, 
as consequent on such structure, that Dicotyledons “ should be 
tolerant of cold,” while Monocotyledons, might be, on the other hand, 
“very susceptible of freezing.” But since Dicotyledons do not 
consist of concentric layers of wood and bark, with a stratum of 
confined air interposed between each of them, but of concentric 
and continuous layers of wood enclosed in a layer of bark, organi¬ 
cally continuous, and without the interposition of any air-stratum 
whatever between any of the layers, we fail to find the structural 
advantage they possess, which would lead us a priori to the conclu¬ 
sion that these plants were specially fitted for cool and moderately 
warm climates. Dr. Daubeny, we think, leaves it to be inferred that 
Dicotyledons especially affect such climates, which is very far from 
being the case, An infinitely greater number of the giants of tro¬ 
pical forests are Dicotyledonous than Monocotyledonous. With regard 
to the comparative rarity of Palms beyond the tropics, it is true they 
do occur only as stragglers in cool climates, but we cannot conceive 
that the internal structure of their stems has anything whatever to do 
with determining the limit of their distribution. The circumstance 
of their growing usually with a single, exposed, continuously unfold¬ 
ing terminal bud might perhaps be alleged as one reason why a warm 
climate is needful to them, but the difficulties of predicating, on 
structural data, the capabilities of plants in respect to climate, and 
the inconsistencies in which we get involved when we attempt it, 
are such that, excepting in cases to which familiar physical causes 
directly apply, we think, in the present state of our knowledge, spe¬ 
culations of this kind are quite useless. What notion the members 
of the Torquay Natural History Society retain of the internal 
structure of Palm-stems it is difficult to say. Dr. Daubeny’s account 
of them applies much better to Tree-ferns, or indeed to young 
branches of the Elder. The “marked difference” in the mode of 
