Horticultural yaricties Arisen Suddenly. 103 
either because they produce no seed or yield too small 
a harvest when self -fertilized or because they cannot be 
artificially fertilized on a sufficiently large scale or be- 
cause the number of seeds produced, even under normal 
conditions, is too small. Moreover one is almost abso- 
lutely confined to annual or biennial species or to such 
perennial ones as flower freely in the first year. 
But in spite of these difficulties and of the incom- 
pleteness of the observations made hitherto, we may 
safely conclude from them the possibility of an experi- 
mental study of the origin of horticultural varieties. 1 
1 1 shall describe an experiment of this kind with Linaria vul- 
gar is pcloria in 20. 
