Theory of Plant Breeding 
“Keep the tubers for one year, then soak them in wine, 
and dry them before they are sown.”” So that it is by 
no means certain that double flowers appear without 
any assignable reason. 
Fasciated stems are sometimes due to injury. If the 
main shoot is cut off when the plant is in full growth, 
then the full current of sap seems to be turned into the 
lateral buds, which grow out as a fasciated stem.® 
Fasciation and torsion or twisting of the stem are also 
said to be inherited.® 
Although there are all these objections to mutancy as 
a theory of evolution, yet there is no possibility of con- 
troverting De Vries’ main position, which is that varia- 
tions do arise in a way that we cannot yet explain. 
Most botanists, however, had fully realised that. 
There is also the fact that, as we have seen (see p. 147), 
it is a mistake to suppose that vegetables are wholly 
passive and inert in the struggle for existence. A 
response made by vegetable protoplasm may not at 
first appear very important, and yet a new enzyme 
might so alter the physiological state of the plant as to 
produce a sudden “mutant.” Botanists are not sup- 
posed to sit down and wonder at such changes but to 
try and explain them. 
Dr. Francis Darwin in his address to the British 
Association (1908) explains another very interesting 
theory so clearly and fully that the reader should refer 
to the original paper. A physiological state (the term 
used by Klebs) is compared by him to a complex habit 
gradually built up by the addition of new complications 
and fixed by continual repetition. 
The botany of to-day has obtained great assistance 
from the experiments of the Abbé Gregor Johann 
Mendel. He was the son of a peasant proprietor at 
Heizendorf bei Odrau in Silesia, and was born in July 
300 
