+t THE FERTILISATION OF FLOWERS. [PART I. 
and acute observations and his pai poe and accurate 
interpretations. 
Instead of the correlation of living organisms, which Sprengel 
had made the subject of observation and reflection with such 
admirable results, classification and afterwards anatomy and 
embryology occupied investigators so exclusively that no one ever 
thought of continuing Sprengel’s beautiful. researches or of 
testing their accuracy. His work remained forgotten until our 
ideas of organic nature were fundamentally changed by the progress 
of knowledge, and until the advantages of cross-fertilisation, which 
Sprengel only faintly realised, were recognised anew and more 
clearly through independent experiments. 
The idea of independent creation of species, prevalent in 
Sprengel’s time and so confidently stated in his book, was overthrown 
by progress in the three departments of classification, embryology, 
and paleontology ; all three led consistently to the conception that 
the existing species of plants and animals must have originated 
from simpler forms; and Darwin’s Origin of Species proved the 
point by deiopaention clearly and thoroughly how actual forces 
were operating before our eyes to modify living forms. 
But, even before this great revolution in our conception of 
nature, one point which was needed to make Sprengel’s theory 
efficient had been clearly perceived. A few years after Sprengel’s 
book appeared, Andrew Knight (392), after some experiments on 
cross-fertilisation and self-fertilisation in the pea, laid down the 
law that in no plant does self-fertilisation occur for an unlimited 
number of generations. But his law received no further atten- 
tion, and nobody conceived the idea of applying it in connection 
with Sprengel’s theory. A like fate overtook Herbert (334), who 
summed up the result of his numerous experiments in this sentence : 
“T am inclined to think that I have derived advantage from impreg- 
nating the flower from which I wished to obtain seed with pollen 
from another individual of the same variety, or at least from 
another flower, rather than with its own” (p. 371). OC. F. Gartner 
(259) was led still more distinctly to the same result by experiments 
on Passiflora, Lobelia, and Fuchsia. Even when Darwin, in 1857 
and 1858, published some new experiments on Papilionaceee (151), 
which showed that the aid of insects or artificial imitation of their 
action was necessary for complete fertility, and that crossing of 
separate plants was actually to a great extent effected by insects, his 
re-enunciation of Knight’s law remained ineffectual. The charm 
that had kept Sprengel’s theories inoperative was only broken when, 
