ed!” | 
PART I. | HISTORICAL INTRODUCTION. 3 
and succeeded in explaining most of their characters as contrivances 
for insect-fertilisation. His theory, although the first effort in this 
wide field, would have afforded a satisfactory key to the chief 
puzzles of the floral world had it not contained a very serious flaw, 
which Sprengel was not conscious of, and was therefore not in a 
position to remove. Since the conveyance of pollen to the stigma 
is obviously of no benefit to the insect, the same question should 
have arisen even from Sprengel’s teleological standpoint, which 
nowadays comes up prominently when we consider his hypothesis 
from the standpoint of natural selection: “What advantage can it 
be to the plant that its pollen should be conveyed by insects to 
the stigma?”’ For just as according to our modern views only 
modifications which are of advantage to their possessor can be pre- 
served by natural selection, so from the teleological standpoint 
only beneficial arrangements could be ascribed to the all-wise 
Creator. If the conveyance of pollen to the stigma by insects is 
of no greater advantage than the direct contact of the reproductive 
organs in the flower, then the preference of the former uncertain 
method to the latter seems unnecessary and capricious, and any 
theory based thereon falls to the ground. 
It is remarkable in how many cases Sprengel recognised that 
the pollen is carried of necessity to the stigmas of other flowers by 
the insect-visitors, without suspecting that therein lies the value of 
insect-visits to the plant. In very many plants Sprengel had 
observed that the two sets of sexual organs in the same flower are 
not developed simultaneously; to this phenomenon he gave the 
name dichogamy. In his introduction (p. 43) he says expressly: 
“Since very many flowers are of one sex only, and probably as 
many more are dichogamous, nature seems to intend that no flower 
shall be fertilised by means of its own pollen,” and as a proof of 
this he adduces an experiment performed by him on Hemerocallis 
Julva, which showed him that this plant is not fertile to its own 
pollen. So near was Sprengel to the distinct recognition of the 
fact that self-fertilisation leads to worse results than cross-fertilisa- 
tion, and that all the arrangements which favour insect-visits are 
_of value to the plant itself, simply because the insect-visitors effect 
cross-fertilisation ! 
But this omission was for several generations fatal to Sprengel’s 
work, which was otherwise well fitted to give a powerful impulse 
to further research. For, both at the time and subsequently, 
botanists felt above all the weakness of his theory, and they set 
aside along with his defective ideas the rich store of his patient 
B 2 
