76 CLASS-BOOK OF BOTANY. 
FLORAL DIAGRAMS. 
An excellent and graphic mode of illustrating many details 
of the structure of a flower is to draw what is called a floral 
diagram. This is really a sort of ground-plan of the flower 
as looked at from above, the parts being represented as if they 
lay on one plane. 
When we make a longitudinal section through a flower we 
obtain a very good idea of the relative position of the floral 
whorls with regard to one another—+.e., of the adhesion of the 
different whorls; but a drawing of such a section does not 
necessarily give much information as to their cohesion, exstiva- 
tion, &c. This can only be graphically represented by the 
floral diagram. Theoretically, the diagram represents the 
appearance of a section taken transversely through a flower- 
bud; but, as sections taken at different heights give different 
appearances, it is necessary to combine these in the figure. 
In drawing these diagrams the pupil should either be 
furnished with coloured pencils or, better still, should adopt a 
certain rule for representing the floral whorls with the ordinary 
pencil. Thus the sepals may always be represented—as 
shown in the diagrams given in this work—by double lines 
transversely shaded; the petals by double lines filled in with 
dark shading; the stamens by figures resembling the anther 
in transverse section; while the appearance of the ovary in 
transverse section may be faithfully reproduced. 
Let us take as the first example of our diagram that of a 
single Pink or Sweet William. In 
commencing, let the pupil draw very 
faintly four concentric circles, the 
largest about 2in. in diameter, within 
which to construct his plan. Now, 
if a transverse section be made through 
the lower part of a flower-bud (after 
removing the bracts) the calyx will 
appear as a single ring, while if it be 
bs made near the top it would oe ap- 
ae. - pear as five very short lines. Dy com- 
= Pink (Dian Stee bining these spnearanrees we represent 
x the calyx, on the outer circle of the 
diagram, by 5 curved lines (ca), whose ends are united to show 
that the cohesion is gamosepalous. If we examine a very 
young bud we find that two of the sepals (1 and 2) are external 
to the others, a third (3) overlaps one of its neighbours by a 
edge, while the two inner (4 and 5) are themselves overlappe 
on both edges: the imbricate nature of the estivation may 
thus be accurately represented. On the second circle the petals 
