PREFACE, : xxvii | 
find a great diversity in the external form; but on scrutinizing the inte- 
rior, particularly the embryo, or the very rudiment of a new plant, we find 
only £wo modifications ; and each of these, after having opened different 
seeds, we perceive to be constant to a very great class of plants united 
together, whether by the structure of the fruit, the number of stamens, 
or by the flower, or by the anatomy of the stems, or by the leaves. 
These modifications of the embryo, resting on there being one or two 
cotyledons, must thus form the groundwork of a natural method : it was 
already foreseen by Linnsus, but was demonstrated by Jussieu. We 
only here allude to those plants in which a seed and embryo exists; for 
- the very principle from which we started implies their existence. A pri- 
mary division, then, pointed out by nature, is therefore obviously into 
those with flowers, and those that have none, or into those which have 
seeds and an embryo, and such as have neither true seeds nor an embryo. 
We have thus a division into Exrembryonate and Embryonate vege- 
tables. The former having no embryo, can have no cotyledons, and are 
often termed Acotyledones ; their stems do not appear to present spiral 
vessels ; hence they are also called Cellulares, and are distinguished into 
those which have tubular vessels or ducts, Ductulose, and those without 
ducts, Eductulose. De Candolle, however, and some other eminent bo- : 
tanists, arrange the Ductulose with the Vasculares. 
The Embryonate vegetables, possessing true spiral vessels, and hence 
called Vaseulares, divide into those with one, and those with two coty- 
ledons, which was no sooner fixed than many corresponding differences 
of structure became perceptible. Thus Monocotyledones shew a radicle 
that projects the root through a covering. The divisions of the flower 
are ternary ; the leaves are curvinerved, primarily alternate or spiral, 
but indicating a disposition to become opposite at the summit of the - 
plant ; the stem is cylindrical, and increases in diameter from within by 
an expansion of the vascular fibre. The Dicotyledones, on the contrary, 
have opposite cotyledones ; the radicle of the embryo becomes a root by — — ; ct 
mere development; the division of the flower is usually quinary; the — 
leaves are angulinerved, and primarily opposite or verticillate, with a 
tendency to become alternate towards the inflorescence; the stem is co- — (T 
nical, with a bark, both increasing by concentric layers, the stem from 
without, the bark from within *. coda a 
. Having thus attained primary divisions with important and constant — 
* To these, as to all general rules, exceptions occur. Thus sometimes, as in the Dico- 
tyledones, the embryo is not distinguishable into cotyledons and radicle: but one of the 
most remarkable cases is to be found among parasitical plants, in several of which, although 
the number and structure of the parts of the flower obviously mark them as belonging 
either to the Monocotyledonous or Dicotyledonous vegetables, the seed appears to be al- 
most or quite homogeneous, and the stems perfectly cellular (without ducts or spiral ves- 
sels), as in the Acotyledones. f sc " dB à; 
c2 
