go ASSOCIATION OF ORGANISMS—THE WEB OF LIFE 
kinds of arrangement we may take the common wild Monkey- 
Musk (Mimulus luteus, fig. 1081) as an interesting example. An 
insect visiting this flower first touches the bilobed stigma, which 
receives any pollen that the visitor may bring. But the stigma is 
very sensitive to contact, and immediately closes, almost like a 
book, remaining in this state for some time. Hence it does not 
receive from its own flower any of the pollen with which the 
departing guest has been loaded. 
It ought, however, to be stated that some flowers are regularly 
self-pollinated, while others exemplify a number of most ingenious 
devices for effecting this as a last resort. The whole structure of 
Zp x 
ZQ>” FBO 
Fig. 1081.—Pollination of Monkey Musk (Af2#e2lus luteus). 1, External view of flower; 2, same in longitudinal 
section, with open stigma; 3, ditto with closed stigma. 4, Pollen is deposited on the lower lip of the stigma by a 
proboscis passing in the direction of the arrow; 5, the stigma has closed, and the proboscis passing on opens the 
closed anthers and becomes covered with pollen; 6, proboscis being withdrawn in direction of arrow, but does 
not deposit pollen on the stigma as this is closed. 1, 2, and 3, natural size; 4, 5, and 6, somewhat enlarged. 
a Foxglove flower, for example, is wonderfully adapted to cross- 
pollination by humble-bees, but after a time the purple corolla falls 
off, and in so doing drags the stamens attached to it over the 
stigma, so that this is self-pollinated, and if it has not already 
received foreign pollen, the egg-cells will be self-fertilized. Full 
details of this sort of arrangement will be found in Kerner and 
other botanical works, but would be out of place here. It is 
perhaps desirable to add that some authorities believe the im- 
portance of cross-pollination to have been somewhat exaggerated. 
DerFENCES OF FLOWERS AGAINST UNBIDDEN GuEsts.—The 
animals which are most serviceable as agents of cross-pollination 
are those capable of carrying pollen from one plant to another, 
though interchange between flowers on the same plant is beneficial 
to a lesser degree, and is often the chief kind of crossing which 
takes place in cases where a considerable number of small flowers 
