22 
JOUENAL OF THE ROYAL HORTICULTUEAL SOCIETY. 
the natural hybrid growing wild in the small lakes of the Black Forest 
and in Lapland, The hybrid is said to be most prolific in situations- 
beyond the range of the parent species. Another instance of the hybrid 
origin of a species, but of which I could not say that it fills a place not 
filled by either parent, is to be found in Medicago meclia^ widely 
cultivated from its own seed as a fodder plant. Its parents are Medicago 
falcala and M. sativa. Interesting experiments have been made with it,, 
and Kerner says that "it would be prejudicial were one of the parent 
species to supply pollen, seeing that the fertility of the hybrid i& 
diminished thereby." 
II. 
Having now dealt, I hope sufficiently, with evolution in nature, the- 
question I have to deal with is whether the same forces are concerned in 
the production of garden species and varieties, and whether those same 
forces do entirely account for garden productions. Of course I recognise 
different circumstances. Variations, for instance, that could not survive 
in nature are preserved by artificial selection in gardens. But, for my 
part, I can only answer that we do get all the field and garden kinds, in 
which we delight and benefit, by the very mechanism which has evolved 
the present flora of the earth. Evolution in gardens is nothing but the 
adopted evolution of nature. It is the same thing, and, though we may 
''touch the button," Nature surely does the rest. 
You will remember my three factors : — 
1. Variation. 
2. The struggle for existence, viz. a sifting process. 
3. The consequent survival of the fittest. 
Variation is rife in the garden, and by altered and varying conditions, 
is even more frequent, perhaps, than it is in nature. All cultivatioiiL 
tends to produce variation. 
The struggle for existence is neither more nor less than a sifting-out 
process, and that is a process familiar to all who know anything of the 
inside of a garden. We are always selecting good stocks for seed, and 
man may be said to do for his purpose precisely what Nature does for 
her purposes. 
The survival of the fittest is the very object and aim of this brain- 
directed sifting-out process, and so I think that the parallel between 
Nature and the garden is very fairly exact. We have an artificial selec- 
tion in the place of natural selection, but both are. governed by natural 
laws and take place in the same way. 
But, I can imagine it said. There is a great difference ; the result is 
different ; all garden productions are unstable ; they revert to original 
species ; your hybrids if not sterile revert in a few generations to the 
original parents. To this I have a double reply. All those things, so 
far as they are true, are equally true of natural productions. Nature 
does not always succeed, so to speak, in her own business. Variations- 
fail; indeed whole hosts of variations must fail to get an initial start; 
and hybrids, too, no doubt fail very often, as they do in gardens. The 
other part of my reply is this, that the allegations are not always 
