34 



STEMS AND BUDS 



Fia. 24. Diagrammatic cross-section of a tree stem showing the medullary rays and 



annual rings. 



FIG. 25. Trees showing the excurrent type of stems. 



along the ground (ground ivy) ; or climbers, as in the case of 

 many vines which cling to other plants, walls or buildings for 

 support. Climbing may be accomplished by twining or by 

 means of specially modified branches or stems (tendrils of 



