14 THE FERTILISATION OF FLOWERS. [PART I. 
I. Plants with Motile Reproductive Elements 
(Zoogame). 
Fucacee, Characez, Protonemez (Mosses and Liverworts), and 
Proembryonatz (Ferns, Horse-tails, Rhizocarps, and Club-mosses), 
whose antherozooids, corresponding to the spermatozooids of 
animals, are endowed with spontaneous movement. Nearly allied 
to these are the Diatoms and Conjugate, in which the whole 
individual is motile. 
II. Plants which require External Aid to bring their 
Reproductive Elements together (Diamesogame). 
A. Plants fertilised by the agency of water (hg ydroplenten 
B. Plants fertilised by the wind (anemophile). 
C. Plants fertilised by the aid of small animals (evidiophite), 
A. Plants Fertilised by the Agency of Water. 
Delpino subdivides this class into two :— 
1, Plants adapted for fertilisation under water. These require 
for cross-fertilisation that the stigma or the poilen-grains, or both, 
should be thin and filiform, and that the pollen should be abundant 
and of like specific gravity to the water (Posidonia, Cymodocea, 
Zostera, Ceratophyllum, Floridec). 
2. Plants adapted for fertilisation at the surface of the water. 
In these the pollen is specifically lighter than water, or is borne 
upon a floating raft ; the peduncles of the female flowers elongate, 
sometimes aided by their spiral form, to bring the flowers to the 
surface of the water (Ruppia, Vallisneria). 
B. Plants Fertilised by the Wind. 
The only positive character common to these is their smooth 
and easily scattered pollen; the negative characters common to 
them are absence of bright-coloured floral envelopes, of perfume, 
and of honey. 
1. The Gymnosperms are all wind-fertilised, and are charac- 
terised by the absence of a stigma. 
2. The anemophilous Angiosperms have for the most part 
enormously developed stigmas, which project in the form of long 
tails, brushes, lamine, or discs; their male flowers are very seldom 
immovable, but are generally easily shaken by the wind, either the 
axis of the male inflorescence, or the peduncles of the male flowers, 
