PART IY. | GENERAL RETROSPECT. 573 
to repeated visits. Hence even well-marked anemophilous flowers 
are often visited by insects.* 
This fact is of special importance in explaining the origin of 
entomophilous flowers. For the fact that the lowest and most 
primitive Phanerogams are anemophilous forces us to suppose 
that all entomophilous plants have sprung originally from anemo- 
philous ; that the first adaptations to insect-visits were attained in 
. flowers adapted for wind-fertilisation; and that wind-fertilised 
flowers, then as now, received visits from insects. In comparatively 
few entomophilous flowers is the amount of pollen required by the 
plant itself the sole attraction for insects. The great majority 
either produce a large excess of pollen or else secrete honey. The 
fact that many plants? secrete honey even outside their flowers, 
in which case it does not influence fertilisation, renders it probable 
that the mere excretion of honey is beneficial, and may have begun 
before all adaptations to insect-visits. Whether the excretion 
of honey began before or after the first adaptations to insect- 
visits, honey is now the most powerful attraction for insects. If 
we compare the insect-visits of Genista and Lotus, of Helianthemum 
vulgare and Ranunculus acris, R. repens, or R. bulbosus, of Spircea 
jfilipendula or S. Ulmaria with 8S. salieifolia, S. ulmifolia, or 
S. sorbifolia, we perceive how much more abundant visits (ceteris 
paribus) a flower which contains honey receives than a similar 
flower which does not, and how much more various are the 
insect-visitors if the honey is-easily accessible. 
A third food material which leads insects to repeated visits 
is sap included within succulent tissues, Darwin’s observations 
and my own have shown beyond the possibility of doubt that the 
inner membrane of the spur of our native Orchises is pierced by 
insect-visitors. I have shown that the same is probably true 
of Cytisus Laburnum, and Erythrea Centaurium. The circum- 
stance that many flies (Hmpidw, Conopidw, Bombylide), as well as 
the more specialised bees and Lepidoptera, are provided with a 
boring apparatus at the tip of their proboscides, indicates, that 
_ this boring for sap is much more usual among insects than was 
formerly supposed. From the comparatively few visits which our 
Orchises receive it would appear that sap included within a tissue 
is less attractive to insects than free honey. 
Anthers, filaments, petals, carpels, in short all the more delicate 
1 See Poteriwm, p. 236; Artemisia, p. 333; Cupulifere, p. 523; Cyperaceer, 
Graminee, p. 567. 
Cf. Vandine and Fpidendrine, p. 528. 
