1478 THE STORY OF THE UNIVERSE 



observed in parts of South America) the vegeta- 

 tion : this again would largely affect the insects ; and 

 this, as we have just seen in Staffordshire, the in- 

 sectivorous birds, and so onward in ever-increasing 

 circles of complexity. Not that under nature the re- 

 lations will ever be as simple as this. Battle within 

 battle must be continually recurring with varying 

 success; and yet in the long run the forces are so 

 nicely balanced that the face of nature remains for 

 long periods of time uniform, though assuredly the 

 merest trifle would give the victory to one organic 

 being over another. Nevertheless, so profound is 

 our ignorance, and so high our presumption, that we 

 marvel when we hear of the extinction of an organic 

 being; and as we do not see the cause, we invoke 

 cataclysms to desolate the world, or invent laws on 

 the duration of the forms of life! 



I am tempted to give one more instance showing 

 how plants and animals, remote in the scale of na- 

 ture, are bound together by a web of complex re- 

 lations. I shall hereafter have occasion to show that 

 the exotic Lobelia fulgens is never visited in my 

 garden by insects, and consequently, from its peculiar 

 structure, never sets a seed. Nearly all our orchid- 

 aceous plants absolutely require the visits of insects 

 to remove their pollen-masses and thus to fertilize 

 them. I find from experiments that bumblebees 

 are almost indispensable to the fertilization of the 

 heart's-ease (Violo tricolor), for other bees do not 

 visit this flower. I have also found that the visits 

 of bees are necessary for the fertilization of some 

 kinds of clover; for instance, 20 heads of Dutch 



