FERTILISATION OF VARIOUS FLOWERS DY INSECTS. 163 
for the fertilisation of the flower is clearly erroneous. Their 
position shows that their use is the very opposite. They serve 
to sweep the pollen out of the way, and prevent it from reach- 
ing the stigma. It would he better, then, to call them polls 
expulseurs than polls collect eurs, by which latter title they are 
known in French manuals. 
As the expansion of the flowers begins at the circumference, 
and thence extends towards the centre, it is plain that the pollen 
of any given flower must be used to fertilise another placed 
more towards the periphery than itself. What, then, of the most 
peripheral of all ? Their pollen can be of no use to flowers in 
the same capital, for none lie outside them. It is intelligible, 
therefore, that these flowers should cease to produce a compara- 
tively useless product ; and accordingly we find the ray-flowers 
destitute of stamens, though still provided with a pistil. As 
there are no stamens there is again no necessity for a brush to 
sweep out the pollen, and accordingly we find that the hair- 
like papillae are quite rudimentary in the style. It is the saving 
thus effected that enables the ray-flower to produce a large 
corolla ; and this again we may conjecture to serve, by the 
brilliancy it gives to the capital, to attract insects.*' The disk- 
flowers by this arrangement are free from any obligation to 
produce a showy corolla, and so have more material at their 
disposal for a plentiful production of pollen. 
This view of ray-function is in harmony with the fact that, 
as a rule, in non-radiate capitals the individual florets are larger 
and more conspicuous than the disk-flowers of a radiate. They 
have to perform for themselves the duty which in the other 
case falls almost exclusively on the ray. It harmonises also 
with the fact, that when either there is an exception to this rule, 
or when in radiates the ray is so small as to add but little to 
the brilliancy of the capital, other means are usually adopted 
to increase the attractiveness. Thus a number of the incon- 
spicuous capitals may be massed into a corymb or a panicle, 
which, in virtue of increased size, appeals more fully to the eye. 
Such, for instance, is the case with Eupatorium . Or the flowers 
may be endowed with a strong aromatic odour, as in Artemisia , 
and insects be thus allured through another sense than sight. 
Or both plans may be combined, as is the case with Tansy. 
Again, what function has the ray, if not that here assigned to 
it ? Perhaps it may be said that it has none ; that it is 
nothing more than the inevitable but useless consequence of the 
staminal suppression; that the primary object of Nature was to 
produce a monoecious condition, which is of known advantage ; 
* That the ray serves to attract insects was held by Sprengel, as I learn 
from “ Origin of Species,” p. 145. Mr. Darwin u does not feel at all sure 
that the idea is so far-fetched as it may at first appear.” 
M 2 
