REPRODUCTION 255 



fatal thing. Again the frost which kills a living herb 

 would produce in another similar but lifeless herb the same 

 injurious mechanical changes, which neither living nor lifeless 

 herb could obliterate or reverse and recover from. Ex- 

 cessive shade or light injure and may be fatal to living 

 plants, the former entailing insufficient food-manufacture, 

 the latter causing undue activity in this or in other ways. 

 Lifeless structures as sensitive to light will also be affected 

 by the same means; the photographic plate is injured or 

 ruined by insufficient or by excessive light. 



From these examples the inference is obvious that, if the 

 conditions which make life possible ( p. 6 ) were maintained, 

 many organisms which now die at the end of a season 

 or a cycle, would continue to live. The inference could 

 not, however, be extended to all plants, because what de- 

 termines the span of life of the organism is often within it, 

 not outside. This every one knows. Wheat harvest comes 

 long before frost or heat or drought can terminate the lives 

 of the wheat plants. In California the wheat plants are 

 dead before harvest begins. They have ceased to live when 

 they have matured their fruits. They have transferred to 

 the embryos in the fruits the life which they themselves 

 possessed. The one living wheat stalk has formed several 

 or many kernels, each containing a living plantlet. Among 

 these new individuals the life of the parent has been com- 

 pletely distributed. The parent stalk ceases to live, its life 

 is ended, the parent lives only in its offspring. No external 

 influences have contributed to the death of the stalk except 

 as they have contributed to its successful life and to its 

 production of successors. So it is with other plants which 

 fruit once and then die, whether fruiting take place in a 

 month, a season, or a "century." By preventing fruiting, 

 man can artificially prolong the life of many such plants. 

 The flowering plants of our gardens are induced to continue 

 blooming and to live longer by being kept from setting 

 seed. By constantly picking the flowers of sweet-pea, pansy, 

 etc., larger, handsomer and more numerous flowers may be 

 had for a longer time than if the life of the individual plant 

 were allowed to pass over into the new individuals repre- 



