20 | THE FERTILISATION OF FLOWERS. [PART I, 
have stated these two laws somewhat as follows: (1) every species 
of animal and plant has, in otherwise similar circumstances, the 
greater prospect of survival in the struggle for existence, the more 
numerous the offspring that it leaves; (2) every individual may, 
under otherwise similar conditions, be preserved the more easily 
in the struggle for existence, the simpler its requirements are. 
He would not then have required to state these laws as axioms, 
for they are seen to be immediate consequences of the theory of 
natural selection. Starting from these two laws, Axell saw in 
every economy of material, space, or time, an improvement in the 
mechanism of the flower. Accordingly he considers the arrange- 
ment in anemophilous flowers the most primitive and most 
imperfect form amongst Phanerogams, since it necessitates an 
immense waste of pollen, which is avoided in cross-fertilisation 
by insects. In both the anemophilous and the entomophilous 
sections, Axell recognises a further advance in the transition from 
dicecious to moncecious and monoclinic forms, since in this arrange- 
ment there is not only increased economy of material (floral 
envelopes, pollen), but increasing certainty of sexual reproduction. 
In the group of monoclinic entomophilous flowers, Axell considers 
that a further advance is shown in passing from dichogamic to 
herkogamic flowers (those in which self-fertilisation is hindered 
by the relative positions of the parts), and from these to the 
heterostylic (dimorphic and trimorphic), and finally from these 
to the homostylic plants with irregular flowers and again to those 
with regular flowers. 
According to Axell, the forms which stand nearest to the diclinie 
entomophilous flowers are the dichogamic,! as in both of these 
types two insect-visits are necessary for each act of fertilisation, 
and many insect-visits which are paid successively to flowers in 
the same stage of development remain useless to the plant. 
Among homogamic entomophilous flowers, the herkogamic, in — 
Axell’s opinion, share with the dichogamic forms the disadvantage 
of not being able to fertilise themselves in case of need; but they 
stand one stage higher, since each act of fertilisation requires only 
a single insect-visit. This is also the case in heterostylic forms, 
which according to Axell stand yet a stage higher, since in them 
self-fertilisation, though very difficult, is not impossible. Finally, 
1 Axell allows the quite unfounded supposition that the corolla begins to wither 
and the secretion of honey ceases as soon as pollen is applied to the stigma to lead 
him into the equally erroneous conclusion that proterandrous dichogamy only is 
possible in entomophilous flowers; and this conclusion leads him. to doubt the 
accuracy of many observations which are opposed to his view, 
