U4 PROBLEMS OF EVOLUTION 



of them, to put a stop to the wastefulness of the primitive wind- 

 fertilisation. The constant tendency to reduce waste makes 

 itself visible everywhere in nature. It is no use objecting that 

 a comparatively simple flower like a buttercup (Ranunculus) is 

 more widely distributed than many orchids that have elaborated 

 the most perfect system of cross fertilisation ; that grasses having 

 once had perfect flowers, which very probably appealed to insects, 

 have lost their petals and their calyx, and trust entirely to the 

 wind ; that fir trees, for all their waste, thrive and multiply 

 wherever the soil and other conditions are suitable ; that cod-fish 

 are caught by the million every year and yet the supply does not 

 fail. All this is true ; nevertheless it is not the whole truth, 

 but only a small portion of it. 



Every species depends for its survival on a number of char- 

 acteristics. Many species of fir trees can grow on hill sides 

 where the soil is scanty, sending out long roots over the rocks 

 till at last they come to a patch of good ground. Their needle- 

 like leaves do not allow a great weight of snow to lodge, so 

 they maintain their foliage throughout the year. When once 

 well established they take the moisture out of the ground, shut 

 out the light and allow nothing to grow beneath them. Once 

 established, they remain unassailable, except by fire or by man, 

 for years. Compare this with an orchid. It too has to make 

 good its claim to remain upon the earth. Owing to the short- 

 ness of its life, the success of its seedlings is of the utmost 

 importance ; its seeds germinate quickly and it finds room for 

 young plants near at hand. It produces a very limited amount 

 of pollen, but succeeds by means of its showy flowers and 

 its nectar as a rule in getting a great number of ovules cross- 

 fertilised. Being very small it takes precautions against being 

 eaten by cattle, and it is, in many cases, I believe, distasteful to 

 them. Its sum total of characters save it from destruction as 

 the fir tree is saved by its sum total. 



As we should expect it is mainly among herbaceous plants we 

 find the most perfect contrivances to ensure cross-fertilisation. 

 The stability and longevity of the forest tree enables it to 

 dispense with many of the shifts and clever devices to which 



