DEGENERA TION. 



97 



debased bisexual form. Its stamens are numerous, 

 and they hang out to the wind, as do also the 

 feathery stigmas in the female flowers, to catch the 

 pollen from neighbouring heads. But the closely- 

 allied Sarigitisorba officinalis (Fig. 30) is evidently 

 an entomophilous variation on the same ancestral 

 form ; for it resembles Poteriiun in every respect 

 except in its flowers, which have very few stamens, 

 enclosed in the purple calyx- tube. This interesting 

 case shows us that when a flower has once lost its 



Fig. 29. — Flower of salad b>tmet 

 {Poienuin sans;iiisorbd)\ green 

 and anemophilous. 



Fig. 30. — Flower of great hiirnet (Saiigut 

 so7-ba offici uiiii); purple and entomophi- 

 lous. 



petals and become anemophilous, it cannot rc-dcvelop 

 them if it reverts to insect fertilisation, but must 

 acquire a coloured calyx instead. The same lesson 

 is perhaps elsewhere enforced by Glaiix maritima 

 among the Primnlacccc^ and by Clematis among the 

 Ranitnailaccce. 



Mr. Darwin remarks that anemophilous flowers 

 never possess a gaily-coloured corolla. The reason 

 is clear. Such an adjunct could only result in the 

 attraction of stray insects, which would uselessly eat 

 up the pollen, and so do harm to the plant. Hence 



II 



