ON THE PROTECTION OF BUDS 89 



continuous with the edges ot the petiole, which appears 

 as a strong midrib to the sheath ; while those of 

 Spergularia are perfectly free from the leaves. 



PROTECTION BY HAIRS 



In other cases buds are protected by hairs. These 

 fall into three main categories : 



1. Hairs which form a felt or fur. 



2. Stiff, bristly hairs. 



3. Glands. 



Many species are glabrous, or hairy, according to the 

 conditions in which they live ; for instance, there is a com- 

 mon English Polygonum which, from growing sometimes 

 on land and sometimes in water, is known as P. amplii- 

 Hum. Land specimens are hairy, especially at the 

 nodes, while specimens growing in water have no hairs. 



It has been suggested that the hairs at the nodes 

 prevent small climbing insects, such as ants, from reach- 

 ing the flower, which they would rob of its honey without 

 rendering any service in return in the way of cross-pol- 

 lination. When growing in water the plant obviously 

 needs no such protection. 



Protection by Fur or Felt 



Hairs forming a fur or felt may act in various ways ; 

 as, for instance : 



1. By warding off excessive moisture. 



2. By preventing too much transpiration. 



3. By protecting the buds from excessive cold. 



