Dee AY ey OM tae ME Ce ee EA, one Oferta ee 
THE FLOWER ; 43 
— It is evident that such a flower may be divided into two 
equal halves in several planes, for a line passing thrones the 
middle of any one petal cuts the 
flower into two exactly similar parts. 
All flowers, however, are not so 
simple : sometimes where we should 
expect to find five stamens, only 
four are present. In cases of this 
kind the place where we should 
expect to find the fifth stamen is 
sometimes indicated by some struc- 

ture; thus, in the figwort, where Fic. 45,—FioraL DIAGRAM 
or a COyctic FLOWER 
only four stamens are present, the — (‘Tyrzp), snowing WHORLS 
position of the fifth is indicated by ov Fuoran Leaves ALTER- 
a distinct scale. (Fig. 123.) 
NATING WITH EACH OTHER. 
In the dead-nettle the fifth stamen is also absent, but the 
position of the other four is such that it is easily seen where 

ne 46.—FLorat DIAGRAM 
OF VIOLET, TRANSVERSE 
SECTION, Mupran PLANE 
MARKED. 
_ The dot indicates the posi- 
tion of the stem. 
the fifth would be if it were 
not suppressed. (See Fig. 130.) 
The suppression of one or 
more parts and the unequal 
growth of others leads to differ- 
ences in the leaves of each whorl, 
and the flower is therefore irregu- 
lar. In the sweet pea, violet, fox- 
glove, dead-nettle, the petals are 
not all the same size or the same 
shape: the corolla is irregular. 
Irregular flowers can be divided 
into two similar halves only in 
one plane. A line passing 
through the flower and the main 
stem represents the median plane 
of the flower; a line drawn at right angles to that the Jateral 
plane. The sweet pea and violet can be cut into two equal 
halves along the median plane alone; this is the usual plane 
of the symmetry of the flower. | 
