RUDIMENTS OF THE NATURAL SYSTEM OF BOTANY. 
37 
elucidation by engaging examples. By these the student's memory is powerfully 
impressed ; and, as with the figures stamped on any ductile material, the more 
forcible the instrument, the less likely is its operation to be effaced. 
It is entirely on this principle that we have entered upon the explication of 
the natural arrangement of plants. In itself, it is not only unalluring, but 
positively repulsive. The collection into a small compass of such an immense 
number of scientific names and technical phrases, all compounded from foreign 
languages, and two of these sometimes arbitrarily associated in the same word, is 
enough to discourage any youth of common capacity from essaying its conversion 
to his chosen purposes. 
Botanical, still more than gardening literature, has an idiom of its own. 
The professors of both, writing and conversing most upon their several favourite 
topics, and to or with individuals of equal attainments to themselves, are too 
often unintelligible to the majority of the reading public. In each of these 
departments we endeavour to avoid such a palpable fault. Accordingly, we shall, 
in the present and ensuing papers, apply popular appellatives to the different 
vegetable organs, except in those cases where a more abstruse term has been 
defined in any previous part of the series. 
Unwilling to indulge in needless iteration, we shall direct the reader to p. 177 
of our last volume, for on account of the first partitions of this classification, and a 
full enunciation of the essential characteristics of the principal sub-class, Exogens. 
As it will be important that these should be contrasted with Endogens, which we 
have now to describe, it may here be repeated that the chief characters of the 
former are their branching stems, in which three separate layers — pith, wood, 
and bark — are discoverable, their finely and irregularly veined leaves, which 
decay and fall at once, and in an entire state, and the decided division of the seeds 
into two pretty equal lobes. 
In all these particulars Endogens are wholly different ; presenting, indeed, 
points of distinction directly the reverse. A transverse section of one of the 
ligneous species of this sub-class exhibits a complete agglomeration of tissues ; no 
line of demarcation being discernible. The bark cannot be recognised from the 
woody portion by any particular property or trace of disjunction, and is simply a 
more compressed and indurated part of the stem. No pith whatever can be seen, 
as the place where this is met with in Exogens is filled with the new woody 
developments. 
Endogens being, for the most part, exotic plants, and denizens of tropical 
climates, have never been satisfactorily examined by botanists. The arboreous 
specimens cultivated in northern Europe are too valuable to be made the subjects 
of experiments, even if their growth w T ere in all respects cognate with what it 
would be in their native wilds. On the other hand, those travellers who have 
passed a long time in places favourable for observation, have frequently lacked 
either time, means, or disposition, for pursuing the inquiry. 
