i 3 2 BIOLOGICAL PROBLEMS 



ticular strain in the generation immediately following-; 

 thus Chilian clover seed tends to produce plants which 

 make very rapid early growth, even when sown in 

 Britain; and it is widely held that certain strains of 

 Red Clover grown near the sea in England produce 

 exceptionally vigorous plants, even when the seed so 

 harvested is sown inland. It is not at all unlikely, 

 therefore, or unscientific, to suppose that seed for 

 different purposes should be harvested in different 

 localities, and I think this assumption is not opposed 

 to modern Mendelian teaching, for Mendelian charac- 

 ters are in many cases " strong potentialities" rather 

 than absolute characters. For instance, you breed a 

 Sugar Beet with a strong potentiality in favour of 

 a high sugar content the amount of sugar will to 

 some extent depend upon the conditions of soil and 

 climate ; and if the potentiality for earliness is affected 

 by the conditions under which a parent seed matured 

 and was harvested, I cannot see why other potentiali- 

 ties, for instance the potentiality for rapid colonization 

 in herbage plants, should not be similarly affected. 



It must not be thought, because I have been so 

 insistent on indigenous plants, that I would, therefore, 

 deem locally exotic or even truly exotic species value- 

 less for the ley. The success of Chicory on lime- 

 less soils in districts where this plant is never found 

 wild shows how useful locally exotic plants may be, 

 while the value of Lucerne in many districts exem- 

 plifies the importance of exotic herbage plants. It is 

 interesting to note, however, that when plants other 

 than those which are locally indigenous are used in 

 temporary leys, it is nearly always necessary to sow 

 in considerable amounts, in order that they may 

 rapidly establish themselves. 



Careful trials should always be conducted on a 

 small scale with plants exotic to a locality before they 



