MESSMATES, MUTUALISTS, AND PARASITES 89 
the slimy visitors crawl, transferring the pollen from one blossom 
to another. 
The Humming-Birds of America, and the little Sun-Birds of 
Africa, which resemble them in appearance, suck nectar while on 
the wing from certain flowers. Regarding bird-pollinated forms, 
Scott-Elliot, who made a special study of the subject in South 
Africa, speaks as follows (in Mature Studies):—“ Many tropical 
flowers, such as the Banana, or the beautiful LodeZa cardinalis, 
are visited by the Sun-Birds and Humming-Birds. A great 
proportion of these flowers have a scarlet colour, and a curved 
tube which exactly fits the head and beak of the bird. Others, 
which are visited by these beautiful and lively creatures, have the 
flowers massed together in large cup-shaped heads, such as the 
Proteas, or Sugarbush of South Africa. The bird stands on 
the edge of this cup and plunges its beak into the mass of honey 
flowers which fills it. There are no bird flowers in the British 
Flora, at least so far as the writer’s knowledge goes; but sparrows 
can be seen to dip their beaks into the heads of the Ragwort, after 
insects, and it is very likely that the flower-haunting habits of the 
Sun-Birds began in this way.” One of the bird-pollinated African 
forms (Melianthus mazor) is represented in fig. 1080. 
Few observations have been made upon cross-pollination by 
mammals, but some tropical Bats are supposed to further the 
transference of pollen, and Kerner suggests that the same kind 
office is discharged by Kangaroos for Dryandra bushes. The 
flowers in the latter case are at a suitable height above the ground, 
and are arranged round the edge of a sort of cup, into which a 
fluid resembling sour milk trickles down from them. It is 
not improbable that the little Long-Snouted Phalanger (Zarszpes 
rostratus, see vol. ii, p. 181) transports the pollen of the flowers 
which it constantly visits. 
Prevention of Self-Pollination.—The various arrangements re- 
lated to cross-pollination have been so evolved that they also, at 
least for some time, prevent self-pollination. It may be that a 
particular flower contains stamens only or a pistil only, and these 
distinct staminate and pistillate flowers may either be on the same 
plant (e.g. Spurges,—£fphorbia) or on different plants (e.g. Wil- 
lows,—Safzx). And even where stamens and pistil are present in 
the same flower the pollen is commonly produced before the stigma 
is mature, or, more rarely, the stigma is first ready. Of other 
