COLONIZATION 325 



relation to seed dispersal. It so happens that the fruit 

 of the Mistletoe is attacked by thrushes and blackbirds 

 in hard winters. Perhaps these birds are grateful for 

 the provision, but the plant is not concerned about their 

 welfare; it looks to itself. The succulent fruit induces 

 the birds to eat it, but when, after the meal, they wipe 

 their beaks in bird fashion on the bough of a tree, they 

 detach adherent seeds, which stick to the bark in a 

 position favourable to germination. Or if the seeds are 

 swallowed they pass, undigested and unharmed, through 

 the bird's body, and if fortune favours, are placed in 

 excrement where they can follow out their not alto- 

 gether noble career. The feeding of the birds is inci- 

 dental ; the real end in view is the dispersal of seed. 



Observation of a multitude of examples confirms the 

 conclusion that the fruit has special relation to the 

 launching of posterity on a successful career. Naturally, 

 in the course of dispersal many fruits, with their con- 

 tained seeds, perish. This is fortunate, for if all seeds 

 developed into plants the earth would not be sufficient 

 to maintain the crowd. That plants should produce a 

 superabundance of seeds is seen to be essential when we 

 realize the risks and chances of loss through consumption 

 by birds, and through failure to reach suitable con- 

 ditions for germination. No stretch of the imagination 

 is required in order that we may appreciate the impor- 

 tant issues that follow satisfactory seed-dispersal. Con- 

 gestion is avoided, and new ground is colonized. Sup- 

 pose even a hundred seeds of a Sycamore were to fall 

 immediately under the spreading canopy of the parent 

 tree; they would probably germinate, but they would 

 not secure sufficient light, air, or moisture for vigorous 



