176 BRITISH PLANTS 
the nearest opening arum, and enter it. The birthwort, 
or Dutchman’s- pipe (Aristolochia), is another fly-trap, 
formed on similar lines to the arum, but in this case it is 
a single flower which acts as a trap, not an inflorescence. 
(Fig. 74). 
Pollination by Animals other than Insects.—In England 
this is negligible. If it happens, it is only accidental. 
In the Tropics, however, sun-birds and humming-birds, 
with brilliant plumage and long, pointed 
beaks, regularly visit flowers for the sake 
of the honey, and indirectly act as 
pollinators. Certain flowers—e.g., Aspi- 
distra—are said to be pollinated by 
slugs. 
Devices for the Prevention of Self- 
Pollination. 
1. The separation of the male and 
female organs (stamens and pistils) in 
space—that is, the stamens are in one 
flower, and the pistil in another. Be- 
tween these any pollination at all must 
be cross, and a pollinating agent is 
necessary to carry the pollen to the 
stigma. Both flowers may occur on the 
same plant, but in different flowers 
Fic. '74.—Lonet- 
TUDINAL SEC- 
TION OF UNFER- 
TILIZED FLOWER 
or Aristolochia. 
(REDUCED.) 
downward- 
pointing hairs ; 
b, perianth; 
c, ovary; d, stig- 
mas; é, stamens. 
(moneecious, Gr. monos, single; ozkos, 
home). They may occur in the same 
inflorescence, mixed with bisexual 
flowers, as in many Umbellifere and 
Composite, or they may occur on dif- 
ferent shoots, as in the hazel. In diceci- 
ous plants (Gr. di, two) the pistillate 
flowers occur on one plant and the 
staminate flowers on another—e.g., willow, poplar, box, 
perennial dog’s-mercury, etc. 
2. Dichogamy (Gr. dichos, apart), the separation of the 
sexes in time—that is, the stamens and pistil of the same 
flower do not ripen together. When the stamens ripen 
first, the pollen is shed before the stigmas are receptive, 
and when the pistil is mature there is no pollen available 
from the same flower. When the stamens ripen first, the 
