Flowers 



The spider orchis succeeded in getting only 6 to 8 per 

 cent, of its flowers fertilised. 



Quite as wonderful are the ways in which flowers 

 arrange their reactions to light and sunshine so that 

 the movements of the stalk at every stage are exactly 

 what suits its purposes best. 



The common Geranium pratense is a very interesting 

 example. At first the flower-stalk grows upwards, then, 

 as soon as the flower develops, its own weight causes it 

 to droop or hang downwards. 



Soon the flower becomes again erect, which is brought 

 about by a response in the opposite direction to the 

 action of gravity, or, as it is called, negative geotropy. 

 Then the flower turns a little so that its petals are nearly 

 in a vertical plane (weight and negative geotropy). 



After flowering the young fruit hangs downwards, 

 but as soon as it is ripe, gravity again stimulates it and 

 the mature fruit is upright and, by the growth of the 

 stalk during its ripening, keeps well above the grasses and 

 herbage, so that it is in the most suitable position for 

 distributing its small carpels. 23 



So by this extraordinary series of fitting reactions, it 

 does what is best for itself at every stage of development. 



Even from this short sketch it will be seen that a 

 modern flower is a very complex product. Its own 

 sensitive protoplasm and the delicate balance of supply 

 and demand between root, stem, leaves, and blossoms 

 are sufficient to explain why changes in sunshine, in 

 rainfall, and in soil should produce slight tentative 

 variations. 



But these variations are not allowed to develop 

 riotously and unchecked. Each attempt has not only 

 to prove itself fit to withstand weather and insect- 

 enemies, but it must be a more alluring enticement to 

 artistic and intelligent insects. 



123 



