511 
Whenever the stamens fall away from the pistil and are de- 
flexed the act of pollination cannot very well take place and the 
bunch sets badly. 
Fias. 9 and 10.—Sterile flowers opening rose-like, 
It sometimes happens that the pistil is altogether absent, and 
as this organ contains at its base the ovaries or germ of the future 
fruit, that absence means permanent sterility. 
¥ia. 11.—Double flowers. 
Other flowers are sterile ow- 
ing to the peculiar way they ex- 
pand. Instead of the petals un- 
folding from the base as shown 
in Fig. 5, they open rose-like from 
the top, and when they thus open, 
there is no jerk and no seat- 
tering of pollen, and consequently 
bad setting; or it happens that 
the stamens remain stuck to the 
petals and are shorter than the 
pistil, and are not able to reach 
up to the gummy secretion on the 
stigma. 
The various floral organs, more- 
over, undergo at times modifica- 
tions which prove obstacles to 
their fertilisation. Thus whole 
bunches are seen to turn into 
tendrils; or, owing to a thickening 
of any one of the floral organs, 
the flower assumes the appear- 
ance of being double. Such 
flowers are always sterile. 
All these structural defects 
are hereditary and liable to be 
transmitted through cuttings, 
hence the importance of eliminat- 
ing such vines from a vineyard by 
grafting on them scions from fer- 
