Theory of Plant Breeding 



" Keep the tubers for one year, then soak them in wine, 

 and dry them before they are sown." 7 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. 8 

 Fasciation and torsion or twisting of the stem are also 

 said to be inherited. 9 



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 Abbe Gregor Johann 

 Mendel. He was the son of a peasant proprietor at 

 Heizendorf bei Odrau in Silesia, and was born in July 



300 



