vi] FIXITY OF POSITION IN PLANTS 97 



a circumstance favouring, and so helping to explain, 

 the prevalence of that type in flowering plants where 

 stamens and carpels are present in the same flower. 

 This juxtaposition makes self-pollination possible, 

 and in many cases probable. There are indeed some 

 flowers which do not open at all : in these self- 

 pollination is virtually a certainty. Such arrange- 

 ments may be held to be a provision against the 

 risk of pollination failing. A higher degree of 

 certainty of setting seed is thus achieved than 

 would be possible by dependence upon extraneous 

 agents. Thus taking a broad view of the matter it 

 would appear that it is ultimately the fixed position 

 which has made hermaphroditism more common 

 among the higher terms of the Vegetable Kingdom 

 than it is among the Higher Animals. 



Following a similar line of thought we may enquire 

 what is the reason for those varied methods by 

 which plants secure the distribution of their seeds. 

 The high importance of that distribution must first 

 be grasped. In order that each germ may have the 

 best chance of growing to maturity, it must on 

 germination take up its position in the soil at such 

 a distance from its fellows as not to compete with 

 them for light or sustenance. In proportion as this 

 is achieved with success there will be provision not 

 only for the maintenance of the race, but also for its 

 spread into regions hitherto unoccupied, with increased 



B. 7 



