FLOWER AND FRUIT 189 
Pollination may be either self or cross. Cross pollin- 
ation is an advantage. Self pollination takes place in 
wheat, wireweed, chickweed, and mallow. Cleistozamous 
flowers must be self pollinated. Cross must take place 
in diclinous (moncecious and dicecious) flowers, as also 
in protandrous and protogynous flowers. Wind 
pollinated flowers are inconspicuous, have much fine 
pollen, and have stamens and stigmas hanging out of 
the flower. Insects are the chief agents. ‘There are 
numerous floral mechanisms to prevent self and effect 
eross pollination, e.g., in primrose, pansy, pea, salvia, 
iris, and orchids. Pronuba pollinates the yuecea, and 
birds the rewa-rewa and clianthus. 
Unsuitable insects are kept off by sticky juices, 
hairs, structure of the flower, and closure. 
Water carries the pollen of vallisneria. 
An Inflorescence comprises all the flowers produced 
on a single flowering axis. The main axis is the 
peduncle, and the stalks of single flowers on many- 
flowered inflorescences are pedicels. Bracts are 
modified leaves that protect the flowers of an inflores- 
cence. A spathe is a large bract, and an involucre a 
ring of bracts. 
The raceme is the commonest indefinite inflores- 
spadix, umbel, and head. Definite inflorescences are 
cence. Others are the corymb, panicle, spike, catkin, 
either solitary or cymose. 
I. Simple Fruits :— 
1. Dry and indehiscent—achene, cypsela, cary- 
opsis, samara, nut. | 
2. Dry and dehiscent—capsule, legume, follicle, 
siliqua, silicula. 
3. Schizocarps, dry, split up into several one 
seeded indehiscent fruits—lomentum. 
4. Suececulent—drupe, berry, pome. 
II. Aggregate fruits or etarios — buttercup 
(achenes), larkspur (follicles), blackberry (drupelets). 
