Practice of Plant Breeding 
brated botanist, De Vries, found a plant of clover in 
which some of the leaves had four and five leaflets. By 
selecting from these clover plants he obtained races in 
which four and five leaflets were the usual character. 
But some of the leaves had six and seven leaflets, It 
is very unlikely that any clover plant in the world 
ever had seven leaflets until De Vries started those 
experiments, 
The second method, that of hybridising, has been also 
found extremely useful in practice. 
Natural hybrids are common enough, and especially 
amongst willows, brambles, and mints, (Long lists of 
natural hybrids will be found in the “Report of the 
Conference on Genetics,” published by the Royal Horti- 
cultural Society in 1906.) 
But they do not seem able to survive under natural 
conditions. Mentha sativa is said to be a cross between 
M. arvensis and M. aquatica, but it cannot hold its own 
in competition with its parent species,” 
All sorts of experiments have been carried out in 
hybridisation. 
One of the most unexpected has been the production 
of odd and strange ferns." The spores of many kinds 
of ferns are all sown together on damp soil. So soon 
as the prothallia are in good healthy development, the 
place is flooded with tepid water for a few minutes, 
Some of the antherozoids (male cells) succeed in reach- 
ing the egg cell of some other kind of fern, and a weird 
but valuable mongrel may be the result. 
In Florida a severe winter may destroy the ordinary 
Mediterranean oranges, but by crossing the valuable 
races with Citrus trifoliata, which is able to resist cold, 
the citranges “ Willits” and “Rusks” have been pro- 
duced, and these are found to be of great value.” 
Amongst other triumphs in this line of research are 
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