upper and lower, are also used to indicate the relative
position of the parts of a flower in reference to the axis of
inflorescence. An axillary flower stands between the bract or leaf which
subtends it and the axis or stem which bears this bract or leaf. This is
represented in sectional diagrams (as in Fig. 275, 276) by a transverse
line for the bract, and a small circle for the axis of inflorescence.
Now the side of the blossom which faces the bract is the

_Anterior_, or _Inferior_, or _Lower_ side; while the side next the axis
is the

_Posterior_, or _Superior_, or _Upper_ side of the flower.

[Illustration: Fig. 275. Diagram of papilionaceous flower (Robinia, Fig.
261), with bract below; axis of inflorescence above.]

[Illustration: Fig. 276. Diagram of Violet-flower; showing the relation
of parts to bract and axis.]

274. So, in the labiate corolla (Fig. 256-258), the lip which is
composed of three of the five petals is the _anterior_, or _inferior_,
or _lower_ lip; the other is the _posterior_, or _superior_, or _upper_
lip.

275. In Violets (Fig. 238, 276), the odd sepal is posterior (next the
axis); the odd petal is therefore anterior, or next the subtending leaf.
In the papilionaceous flower (Fig. 261, and diagram, Fig. 275), the odd
sepal is anterior, and so two sepals are posterior; consequently, by the
alternation, the odd petal (the standard) is posterior or upper, and the
two petals forming the keel are anterior or lower.

Sec. 5. ARRANGEMENT OF PARTS IN THE BUD.

276. =AEstivation= was the fanciful name given by Linnaeus to denote the
disposition of the parts, especially the leaves of the flower, before
_Anthesis_, i. e. before the blossom opens. _Praefloration_, a better
term, is sometimes used. This is of importance in distinguishing
different families or genera of plants, being generally uniform in each.
The aestivation is best seen by making a slice across the flower-bud; and
it may be expressed in diagrams, as in the accompanying figures.

277. The pieces of the calyx or the corolla either overlap each other in
the bud, or they do not. When they do not overlap, the aestivation is

_Valvate_, when the pieces meet each other by their abrupt edges,
without any infolding or overlapping; as the calyx of the Linden or
Basswood (Fig. 277).

[Illustration: Fig. 277. Diagram of a flower of Linden, showing the
calyx valvate and corolla imbricate in the bud, etc.]

_Induplicate_, which is valva