Page 167 - Biology_F5

Biology for Advanced Level Secondary Schools

Procedure for construction of a floral (h) The edges of fused sepals or petals are
diagram connected by lines.
(a) In drawing a floral diagram, it should (i) The two lips of bilabiate calyx or
be noted that different floral whorls are corolla are joined by bulging lines.
always represented in concentric circles
starting with sepals on the outermost (j) In epipetalous flowers, where stamens
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circle, followed by petals, stamens and are fused with petals, both whorls are
carpels towards the inner side. linked with small radial lines.

(b) Examine mature floral buds and pluck (k) Count the number of stamens; note
them off the mother axis after noting their cohesion and adhesion to other
the anterior and posterior sides. floral parts and position in relation to
petals, introse or extrose position; and
(c) The floral parts are drawn in a floral draw them inside the petals in the floral
diagram, as they would appear in their diagram. Stamens are represented by
transverse sections below the mother transverse sections of anthers (Figure
axis. A small circle is drawn above the 3.39). Introse stamens face towards the
floral diagram to designate the mother centre, while extrose ones face towards
axis; however, for the terminal flowers, the petals. Staminodes are represented
this circle is not shown. by an asterisk (*) or by a cross (x).

(d) In flowers associated with bracts
(bracteate flower), a section of bract Posterior side
is drawn. In contrast, in bracteolate Plant axis
flower, the bracteoles are drawn in Diagonal plane
section on the left and right sides of Gynaecium
the diagram.
Lateral or Androecium
(e) The number of sepals and their transverse Corolla
arrangement in relation to the mother
axis or aestivation are drawn in Calyx
transverse sections. The odd number
of sepals and petals are drawn either Bract
posterior or anterior to the flower (that
is, opposite the mother axis or opposite Figure 3.39: The floral diagram with labeled
the bract, respectively) with its sepals symbols
and petals alternating.

(f) In zygomorphic flowers, sepals and Floral formula
petals with unequal size are drawn. This is a representation of various floral
parts using standardised symbols and
(g) The spurred sepals or petals are shown numbers. It depicts floral information
by drawing a loop at their respective pertaining to symmetry; floral whorls,
back. namely calyx, corolla, androecium and

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