24 DUNCAN, ON TRIGIDIA. 
processes of the upper part of the axis are vastly increased in 
activity, the tissue swells, and the nutrition of the perianth, 
the style, and the filaments of the stamens, is interfered with 
by a pressure from within outwards, which diminishes the 
calibre of their cells and vessels. The ruin of the flower is 
clearly produced, in part, by the increase in calibre of the 
lower part of the style and the upper part of the axis. The 
balance between the rapidity of the pollen-tube growth and 
the development of the micropyle of the embryo-sac is, of 
course, exact when the impregnation is being perfected, and 
it is the chance of this balance being incomplete which ren- 
ders fertilisation by strange pollen generally so difficult. The 
influence of the female organ in nourishing the male element 
is very suggestive. 
