ioo NATURE OF BUDS 



after a few years but not infrequently they remain alive and 

 become overgrown by the increase of the stem. In such cases 

 the bud grows slowly and maintains itself near the surface of 

 the wood. These buds growing and often branching in the wood 

 produce those curlings and twistings in the grain that are com- 

 monly known as bird's-eye wood. Dormant buds sometimes de- 

 velop into normal branches, as when a portion of a tree is re- 

 moved and consequently an additional supply of food stimulates 

 them to growth. Buds may also arise upon any part of the 

 stem, root or leaf. These are the so-called adventitious buds 

 and their formation upon roots often accounts for the colonial 

 habit of many trees, plants and shrubs, as in the poplars, Ailan- 

 thus, sumacs, etc. They appear to rise naturally in some cases, 

 but in other instances their formation is due to the stimulus of 

 a wound or some other cause and like the dormant bud they serve 

 to prolong the life of the plant. Richards has shown that when 

 living cells are exposed to the oxygen of the air, owing to a 

 wound, that these cells are stimulated as a result to renewed 

 activity. .This doubtless explains the formation of callus and 

 the healing of wounds, as well as the formation of adventitious 

 buds in many cases. Common examples of buds due to wounds 

 are seen in the vigorous shoots that spring up from the stumps 

 of hard wood trees, pollarded willows, etc. Some buds become 

 fleshy owing to the storage of the food and dropping from the 

 plants serve to propagate new individuals. Examples of this 

 are seen in the fleshy buds on the tips of the branches or in the 

 axils of the leaves of the stone-crop and some lilies and in the 

 flower clusters of some onions. Many aquatic plants have the 

 habit of forming similar buds on the approach of winter. These 

 being compact and heavy with food sink to the bottom of the 

 ponds in the fall and renew their growth in the spring. 



