312 LUTHER BURBANK 



case a given stock of daisies — is at all times sub- 

 ject to the unceasing influence of the conditions 

 of life in the midst of which it exists. The whole 

 series of influences which we describe as the envi- 

 ronment is perpetually stamping its imprint on 

 the organism somewhat as the vibrations of light 

 stamp their influence on a photographic plate. 



Indeed, as I conceive it, the plant is in effect a 

 photographic plate which is constantly receiving 

 impressions from the environing world. 



And the traits and tendencies of the plant that 

 are developed in response to these impinging 

 forces of the environment are further compara- 

 ble to the image of the photographic plate in that 

 they have a greater or less degree of perma- 

 nency according to the length of time during 

 which they were exposed to the image- forming 

 conditions. 



If you expose a photographic plate in a mod- 

 erately dim light, let us say, for the thousandth 

 part of a second, you secure only a very thin 

 and vague negative. But if, without shifting the 

 scene or the focus of the camera, you repeat 

 the exposure again and again, each time for only 

 the thousandth of a second, you will ultimately 

 pile up on the negative a succession of impres- 

 sions, each like all the rest, that result in the pro- 

 duction of a strong, sharp negative. 



