ng traced, something may be
inferred as to their real nature from their position in regard to the
other parts of the flower, from their anatomical structure, and from
analogy or comparison with like organs in other plants. The period of
their formation is, perhaps, of less importance than was at one time
supposed, since it is well ascertained that, in some cases, the
formation of the parts of the flower, _e.g._ the stamens of mallows,
follows a centrifugal rather than a centripetal order.

In the case of monstrous developments of this nature too much care can
hardly be exercised, and the observer should rarely venture on an
explanation of the nature of the case from the evidence afforded by the
monstrous growth apart from that to be derived from the study of the
development and organization of the normal flower and from analogous
formations in allied plants.

=Excrescences from axile organs--Warts.=--In a preceding paragraph the
formation of gnaurs has been alluded to. There are other outgrowths,
called warts, occasionally met with in trees, and which are more closely
connected with the central tissues of the stem, while at the same time
they are not provided with buds, in which two particulars warts differ
from gnaurs.

Excrescences of this kind often attain a very large size, and may be
seen on old elms and other trees, but, as their formation is probably
more pathological than teratological, no further notice of these
structures need here be given. No special notice need here be taken of
the tubercles on the roots of so many _Leguminosae_, nor of the peculiar
excrescences on the roots of _Taxodium distichum_, as these appear to be
normal formations. But it may be well to mention in this place an
anomalous development which occurs occasionally in _Ruscus aculeatus_,
and in which, from the upper surface of the ordinary flattened leaf-like
branch, projects at right angles a second similar branch, so that in
section the appearance would be like that of the inverted letter t;
thus, [Symbol: Inverted upper-case T].

=Enation from foliar organs--Leaves.=--The development of adventitious
lobes from leaves may take place either from their surfaces or their
margins. A few illustrations may be given of each. In cabbage leaves a
formation of adventitious laminae projecting at right angles from the
primary one may frequently be observed. In the instance figured (fig.
210) the new growths proceeded almost exclusively from the