20 PHARMACEUTICAL BOTANY 



Leaf buds develop leaves. 



Flower buds are unexpanded blossoms. 



Mixed buds contain both flower and foliage. 



As to position buds are either terminal or axillary, either located at 

 the apex of the stem or branch or in the axils of the leaves. If they 

 occur on other situations on the stem, or upon roots or leaves they are 

 termed adventitious buds. If, as often happens, more than one bud 

 forms in or near the axil of the leaf, it is called an accessory bud. 



The Stem 



The stem is that part of the plant axis which bears leaves or modi- 

 fications of leaves and its branches are usually arranged with mathe- 

 matical regularity. 



The functions of a stem are to bear leaves or branches, connect 

 roots with leaves, and conduct sap. 



When the stem rises above ground and is apparent, the plant is 

 said to be caulescent. 



When no stem is visible, but only flower or leaf stalks, the plant is 

 said to be acaulescent. 



Stems vary in size from scarcely one-twenty-fifth of an inch in 

 length, as in certain mosses, to a remarkable height of 400 ft. upward. 

 The giant Sequoia of California attains the height of 420 ft. 



Direction of Stem Growth. — -Generally the growth of the stem is 

 erect. Very frequently it may be : 



Ascending, or rising obliquely upward. 



Reclining, or at first erect but afterward bending over and trailing 

 upon the ground. Ex. : Raspberry. 



Procumbent, lying wholly upon the ground. 



Decumbent, when the item trails and the apex curves upward. 

 Ex. : Vines of the Cucurbitaceas. 



Repent, creeping upon the ground and rooting at the nodes, as the 

 Strawberry. 



Stem Elongation. — ^At the tip of the stem there is found a group of 

 very actively dividing cells (meristem) which is the growing point of 

 the stem. All the tissues of the stem are deri\-ed from the cells of the 

 growing point whose activity gives rise in time to three generative 

 regions which are from without, inward: 



(i) Dermatogen, forming epidermis; 



