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ORGANOGRAPHY. 
BOOK I. 
fibrils that accompany them ; as in many 
terrestrial Orchidaceous plants, Dahlias, &c. 
These must not be confounded either with 
tubers or bulbs, as they have been by 
some writers, but are rather to be co 
sidered a special form of the root, to which 
the name of Tuhercules {Jig* 46.) would not 
be inapplicable. In Orchis the tubercules 
are often palmated or lobed ; in the Dahlia, 
and many Asphodeleae, they hang in clusters, or are fasci- 
culated. 
In internal structure the root differs little from the stem, 
except in being often extremely fleshy ; its cellular system 
being subject to an unusually high degree of developement 
in a great many plants, as the Parsnip, and other edible 
roots. In Endogens, the mutual arrangement of the cellular 
and vascular systems of the root and stem is absolutely 
the same ; but in Exogens, there is never any trace of pith in 
the root. 
Sect. IV. Of the Appendages of the Axis, 
From the outside of the stem, but connected immediately 
with its vascular system, arises a variety of thin flat expan- 
sions, arranged with great symmetry, and usually falling off 
after having existed for a few months. These are called, 
collectively, appendages of the axis ; and, individually, scales, 
leaves, bracts, flowers, sexes, and fruit. They must not be 
confounded with mere expansions of the epidermis, such as ra- 
menta, already described (p. 63.), from which they are knowui 
by having a connection with the vascular system of the axis. 
Till lately, botanists were accustomed to consider all these as 
essentially distinct organs ; but, since the appearance of an 
admirable treatise by Goethe in 1790, On the Metamorphoses 
of Plants, proofs of their being merely modifications of one 
common type, the leaf, have been gradually discovered ; so that 
that which, forty years ago, was considered as the romance of 
