82 THE FLOWERING PLANT. 
The relation of parts in a flower to one another and, in a 
lateral flower, to the main axis is conveniently represented by 
a floral diagram which may be regarded as a generalized ground- 
plan (fig. 38). The position of the axis is shown by a dot; the 
sepals, petals, and stamens are represented by conventional 
marks ; and the carpels by a rough drawing of their appearance 
in cross-section. A line drawn 
through the axis dot and the centre 
of the diagram serves to represent 
the median or antero-posterior plane, 
which divides the flower into right 
and left halves. A line running 
through the centre of the diagram 
perpendicular to the first line there- - 
fore represents the lateral plane, a 
vertical plane at right angles to the 
Fic. 38.—Floral Diagram of White Lily. median ; plane, which divides the 
st. stem on posterior side of flower; flower into a posterior half next 
Hames ob PL oblique planes; 1, 1, the axis and an anterior half turned 
x. sepals; 2, 2, 2. petals; 3, 3, 3. away from it. Two oblique vertical 
Me ea A ietitee, planes intersecting the preceding at 
nating whorls. 45 degrees may also be represented 
in the diagram. It may seem unnecessary to distinguish so many 
imaginary planes, but it is very convenient in practice to designate 
particular parts of the flower as anterior, posterior, or oblique. 
In the Pea-flower family, for example, there are five sepals, of 
which one is always anterior. ‘This is, therefore, one of the 
distinctive features of the family. 
A study of the innumerable sorts of flower actually existing 
shows that for cyclic forms the most typical condition consists in 
the possession of six whorls, all the whorls having the same 
number of parts, and the parts of successive whorls alternating, 
just as in decussate foliage leaves. Such a flower, say, with five 
members per whorl, can be represented either by a floral diagram, 
or as follows, the dashes representing the floral leaves, which are 
supposed to be picked off and laid in straight lines :— 
——— “Pepe. 
kin Teas Eablet ey seers AS ae Petals. 
pens 
(inner). 
Carpels 
(outer), 
Carpels 
(inner), 
—|f 
—- — -— + = 
| 
| 
