The External Features of Stems 



121 



Fig. 68. A hackberry (Celtis occidciiUdis}. -huviiiL; k liquescent 

 stem. This tree is growing on the open prairie in Illinois. Through 

 the development of the lateral buds, the central stem has been 

 lost in the branches. 



develop each year. This accounts for the basal branching of 

 these plants. 



Excurrent and deliquescent stems. When trees have strong 

 terminal buds, the main stem extends to the top and is called 

 excurrent (Latin: excurrens, running out). The spruce has a 

 strong terminal bud, and just beneath it a whorl of several smaller 

 lateral buds (Fig. 71). The terininal bud grows upward, and 

 the lateral buds grow outward, forming a whorl of branches at 

 the base of the season's growth. This is repeated each year, the 

 terminal shoot lengthening the stem and the lateral buds adding 

 a new whorl of branches. Consequently each year's growth is 



