THE SHOOT. 89 



There are many cases in which the lateral buds are not 

 found precisely in the axils of the leaves, but slightly to one 

 side, or at a greater or less distance above the axil (figs. 99, 

 100). 



106. Extra-axillary buds. — Buds are frequently formed 

 without any relation whatever to the leaf-axil, and even on 

 the leaf itself (fig. 293). Sometimes these extra-axillary 

 buds are produced without the action of any extraordinary 

 cause, but more commonly injury of one sort or another 

 seems to act as a stimulus to the production of such buds. 

 Buds which do not originate in acropetal succession on the 

 parent shoot are called adventitious buds. 



107. Adventitious buds may arise upon stems, leaves, or 

 roots. They are most commonly and abundantly produced 

 upon stems and roots. In the willows their ready production 

 is utilized for obtaining young, vigorous, and pliable shoots 

 to be used in basket-work. The few plants which produce 

 adventitious buds upon leaves, as well as the many which 

 produce them on stems, are often propagated in this way. 

 (See 1 364.) 



108. Dormant buds. — Many buds continue to grow with- 

 out interruption from the time of their formation, but more 

 cease to develop after they have reached a certain stage. 

 Such buds may remain dormant for a considerable period, 

 and may even be overgrown and completely enclosed by the 

 wood upon old shoots. The bud in this case grows slowly 

 and maintains itself near the surface of the wood. It is quite 

 possible that these dormant buds should for some reason 

 begin to develop later, when they are liable to be confounded 

 with adventitious buds. In case they have been buried by 

 the growth of tissues over them, the shoot which they pro- 

 duce will seem to come from the interior of the organ upon 

 which they are borne. This apparent internal origin must 

 not be confounded with the real endogenous origin of roots. 



