858 FLORA AMERICZ BOREALI-ORIENTALIS. 
botanists of well-deserved reputation, who have paid much attention 
to theoretical morphology, Professor Duval and his pupil, Professor 
Moquin-Tandon, and was first applied to the case of floral envelopes 
which appear to have a tendeney to separate into two layers, an inner 
and an outer one, and thus to valine, as it were, which may be given 
as the literal meaning of the word dédoubler ; but it has been gradually 
extended to all cases where any number of floral organs occupy the 
place normally taken by a single one. This phenomenon, which has 
only recently been generally comprehended, and is particularly attended 
to by Dr. Asa Gray, is of great importance in explaining the morphology 
of the flower; but we think that the mode in which it takes place is 
far from being satisfactorily explained by the statement that it is always 
by deduplication. 
In a normal regular flower, it is universally admitted that each sepal, 
petal, stamen, and carpel is an axile appendage of the same morphologi- 
cal nature as the stem-leaf, and to which we therefore morphologically 
extend the term leaf. Therefore, in investigating the various anomalous 
developments which we observe in any one set of axile appendages, we 
must carefully compare them with analogous anomalies of the leaf in 
every tensor Sehin stem-leaf to the 
stem-leaves show a very strong development of the vascular 
system in the ipea of petiole, ribs, and veins, and iu many instances a 
great readiness to produce from it convex or scutelliform glands.* 
These occur most frequently at the top of the petiole or near the base 
of the limb, one or more on each side, or on the surface of the petiole 
or principal veins near the base of the limb: they are also found occa- 
sionally at the end of the midrib or lateral veins, or will break out 
irregularly at any part of the petiole, ribs, or veins. The general surface 
of the leaf will only produce hairs, aculei, or other appendages of the 
cellular tissue, except in cases of disease or monstrosity, where an ex- 
traordinary flow of sap will induce the formation of foliaceous appen- 
dages or regular buds on the margin or on any part of the surface. But 
as these cases are as frequently further depattures from what may be 
termed the normal state, as approaches to it, great care should always 
be taken in adducing them in support of pilosa theories. 
* We advert to the true glands, which always appear to be in close connection 
to be 
= the vascular system, not to those vesicles of essential oil scattered through the 
tissue, which are also designated by the name of glands. 
