110 CLASS-BOOK OF BOTANY. 
in possessing leaves, presumably because its vessels, pene- 
trating into the internal tissues of the host, abstract from it 
unassimilated sap on its way from the root to the leaves, 
which sap the parasite has to assimilate in its own leaves. 
Fig, 216, Viscwm lindsayti, (a) a Mistletoe parasitic on (b) a Rata— 
Metrosideros hypericifolia. 
The modifications of the different parts of the flower have 
been somewhat fully referred to under the different types. 
To recapitulate briefly: The function of the calyx appears to 
be protection ; that of the corolla chiefly attraction of insects ; 
of the stamens the production of pollen which contains the 
male fertilising element ; and of the carpels the production of 
ovules which contain the female element. 
Probably sepals have been developed from ordinary foliage- 
leaves, as may be inferred from their position, form, and 
(usually) green colour; hence their union into a synsepalous 
calyx is a later development. Occasionally, as in Fuchsia,» 
they become petaloid and coloured, the petals being corre- 
spondingly reduced in size; in some genera (Clematis, Ane- 
mone, &c.) the petals are completely replaced by them. They 
are frequently persistent, and either act as protection to the 
fruit (Veronica), or become succulent and brightly coloured 
(Snowberry). In composites and a few allied plants the 
calyx is modified into a pappus. 
The petals have probably been developed from stamens—at 
least, this view is strongly supported by the fact that in culti- 
vation stamens usually tend to turn into petals, and this 
occurs normally in many roses, water-lilies, &e. The great 
diversities of form and colour found in the corollas of different 
plants, and which serye—along with their scent and develop- 
