190 Mr. W. Murton Holmes on the 
access to the interior, but once inside they are caught like a 
mouse in a wire-trap. The stigmas of these flowers are ready to 
receive pollen on their entrance, and if they have previously 
visited a similar flower they are covered with pollen, which 
becomes attached to the stigmas as they crawl over them. After 
a day or two the stigmas fade, the anthers then ripen and dis- 
charge their pollen, covering the imprisoned insects. The hairs 
which prevented the return of the insects now wither, leaving an 
opening for them to escape. Other flowers are then visited with 
the same result. 
Some plants, such as the primrose, have two forms of flowers, 
others have three forms. In one form the stamens are long, and 
appear at the throat of the corolla, while the style is short. In 
the other form the style is elongated, so that the stigma projects 
from the throat of the corolla, and the stamens are short. To 
ensure fertilization the pollen of one form must be placed on 
the stigma of the other, and this is brought about by means of 
insects. 
Interchange of position of anthers and stigmas is another 
contrivance frequently met with. The common pink is an 
example. The stamens are first developed, and, after shedding 
their pollen, the stigma begins to grow, and to occupy the 
same position, projecting beyond the throat of the corolla. An 
insect that has visited a flower in the early stage must in- 
evitably deposit the pollen on the stigma of the flower when in 
the later stage. 
The grass of Parnassus is another example. Here there are 
five anthers, each of which in turn occupies the centre of the 
flower, and after discharging its pollen bends back out of the 
way. An insect in search of honey alights on the centre of the 
flower, and is certain to rub its proboscis against the particular 
anther which has that day set free its pollen, and will thus con- 
vey some of it to a flower in which the pistil has developed. 
In Geranium pratense the anthers open and expose their pollen 
in turn at the centre of the flower, whilst the stigmas still 
remain folded together ; but as soon as these begin to separate 
the anthers fall off, and the mature outspread stigmas are sur- 
rounded only by the needle-like filaments, 
The manner in which insects are sprinkled with pollen when 
visiting the violet is peculiar. The flower is irregular, and has 
its mouth directed sideways. The cone of anthers is set over the 
lowest petal, which is prolonged at the back into a hollow spur 
containing honey. In this spur is a prolongation of the anthers. 
in order to suck the honey a bee must push under the cone and 
run its proboscis along the channel of the spurred petal, where 
it disturbs the spur of the anthers, and its proboscis is imme- 
diately sprinkled with pollen. On its entrance any pollen which 
