Polycephalic Poppies 389 



bility slowly and gradually decreases, to end 

 with the definite decision of aU further growth 

 sometime before the outer form of the organ be- 

 comes visible imder the microscope. The last 

 period of life includes only an expansion of the 

 tissues, which may still have some influence on 

 their final size, but not on their form. This 

 has been definitely arrested before the end of 

 the sensitive period, and ordinarily before the 

 com.TTi encement of that rapid development, 

 which is usually designated by the name of 

 growth, as contrasted with evolution. 



Within the seed the evolution of the young 

 plant manifestly depends upon the qualities 

 and life-conditions of the parent-plant. The 

 stronger this is, and the more favorable circum- 

 stances it is placed under, the more food will be 

 available for the seed, and the healthier wUl be 

 the development of the embryo. Only well- 

 nourished plants give well-nourished seeds, and 

 the qualities of each plant are for this reason 

 at least, partly dependent on the properties of 

 its parents and even of its grandparents. 



From these considerations the inference is 

 forced upon us that the apparently hereditary 

 differences, which are observed to exist among 

 the seeds of a species or a variety and even of a 

 single strain or a single parent-plant, may for 

 a large part, and perhaps wholly, be the result 



