VI] FIXITY OF POSITION IN PLANTS 89 



under which the stationary plant suffers as compared 

 with the freely mobile animal are four: (1) difficulties 

 of self-protection against animal attack, and (2) against 

 climatic conditions : (3) difficulties in effecting polli- 

 nation and intercrossing, and (4) in the distribution of 

 the new germs when produced. These will severally 

 be considered, and the methods will be explained by 

 which plants have met the problems raised by their 

 immobility. 



The stationary plant is the natural victim of the 

 mobile herbivorous animal, and in many cases, such 

 as the ordinary pasture grasses, clover, oi* plantain, 

 there are no special means of defence. The cater- 

 pillar, the slug, and in tropical countries the leaf- 

 cutting ant all take their toll, as well as the larger 

 grazing animals, and frequently without any reprisals. 

 The only resource of the victim is to restore by 

 renewed growth as quickly as possible the parts that 

 have been lost. The animal, on the other hand, which 

 is the victim of a predatory attack has the chance of 

 escape by a combination of wariness and speed, but 

 this is denied to the fixed plant. Other means, 

 however, of protection of the plant against predatory 

 animals exist, and are effective. Some plants, such 

 as the Spurges and Asclepiads, contain distasteful 

 substances in their milky juice : others, such as the 

 Dock and Wood-Sorrel, and some Begonias are 

 protected by their acid taste : others such as the 



