THE COMMON ARUM 



birds are so constituted that what is poisonous to 

 man and other animals is not always so to them. 

 Thrushes, for example, devour the arum berries 

 with impunity, but at the same time there are 

 man}^ smaller birds, such as robins, and large 

 animals, not to mention man, to whom these 

 same berries would probably prove fatal. Most 

 likely the fact is that the arum speciall}^ caters 

 for JDirds of the thrush class that consume its 

 fruits and convey its seeds far and wide, and not 

 for nibbling animals, such as mice and squirrels, 

 which might do the seeds an injury. As the 

 plant has slowly evolved those poisonous pro- 

 perties which prevent undesirable animals from 

 munching its seeds, the thrushes, which best 

 serve the purpose of distribution, have kept even 

 pace in the development of a power to resist 

 the poison ; like confirmed opium-eaters, they 

 may now safely consume quantities of poison 

 that would mean death to others. 



Let us suppose, however, that a small animal 

 or bird should eat such berries and thereby lose 

 its life. The plant would then gain at the ex- 

 pense of the animal, for the decaying remains 

 would offer advantages to the developing plant 

 after the seed had germinated. By the law of 

 heredity, too, the succeeding generation of arums, 

 on account of this advantage, would develop still 

 stronger poison in their berries, which would be 

 still more attractive in appearance. 



Such, then, is the brief history of a very 

 common British plant, and a common plant 



45 



