1883.] Flowers and Insects. 217 
rapidly as will be the case in soils poor in organic 
matter. 
It is curious to contrast the conclusions of M. Deherain 
with, e.g ., the views of Jethro Tull, who maintained that 
the fertility of a soil was capable of being improved and 
maintained indefinitely by constant turning over and pul- 
verisation. 
V. FLOWERS AND INSECTS. 
By J- W. Slater. 
/SkjVNE of the most popular and interesting portions of the 
New Natural History is that which discusses the 
^ relations between flowers, on the one hand, and 
inserts and certain birds on the other. But its very interest 
and importance, not less than the support which it lends to 
the Doctrine of Descent, secure for it in some quarters an 
obstinate opposition. This hostility, as might be expected, 
is met with chiefly in France, where official science and 
alethophobia still shut their eyes to the constantly accumu- 
lating evidence in favour of Evolution. 
The case, as presented by Darwin and his followers, is 
this : — It has been experimentally proved that in plants the 
close relationship of the sexual cells is unfavourable to the 
reproduction of the species. If the pollen of a flower has 
been applied to the stigma of the same flower (self-fertilisa- 
tion) the seeds will prove less productive and give rise to 
less vigorous plants than if they had been “ cross-fertilised ” 
— i.e. 9 if there had been applied to them the pollen either of 
a different flower of the same plant or of a flower of another 
plant. It is, further, beyond dispute that in many flowers 
there exist formal obstacles to self-fertilisation which might 
even be regarded as special contrivances for its prevention. 
Sometimes the male organs of a flower come to perfection 
not at the same time with its female organs, but either 
sooner or later, so that the stigma can only be acted upon 
by pollen from some other flower. In other cases there are 
mechanical arrangements which prevent the pollen of a 
vol. v. (third series). q 
