36 MORPHOLOGY OF STEMS AND BRANCHES. [LESSON 6. 



LESSON VI. 



MORPHOLOGY OF STEMS AND BRANCHES. 



83. THE growth of the stem in length, and the formation of 

 branches, have been considered already. Their growth in thick- 

 ness we may study to more advantage in a later Lesson. The very 

 various forms which they assume will now occupy our attention, 

 beginning with 



84. The Forms of Stems and Brandies above ground. The principal 



differences as regards size and duration have been mentioned before 

 (41); namely, the obvious distinction of plants into herbs, shrubs, 

 and trees, which depends upon the duration and size of the stem. 

 The stem is accordingly 



Herbaceous, when it dies down to the ground every year, or after 

 blossoming. 



Suffrutescent, when the bottom of the stem above the soil is a 

 little woody, and inclined to live from year to year. 



Suffruticose, when low stems are decidedly woody below, but 

 herbaceous above. 



Fruticose, or shrubby, when woody, living from year to year, and 

 of considerable size, not, however, more than three or four times 

 the height of a man. 



Arborescent, when tree-like in appearance, or approaching a tree 

 in size. 



Arboreous, when forming a proper tree trunk. 



85. When the stem or branches rise above ground and are ap- 

 parent to view, the plant is said to be caulescent (that is, to have a 

 caulis or true stem). When there is no evident stem above ground, 

 but only leaves or leaf-stalks and flower-stalks, the plant is said to 

 be acaulescent, i. e. stemless, as in the Crocus, Bloodroot, common 

 Violets, &c., and in the Beet, Carrot, and Radish (Fig. 59), for the 

 first season. There is a stem, however, in all such cases, only it 

 remains on or beneath the ground, and is sometimes very short. 

 Of course leaves and flowers do not arise from the root. These 

 concealed sorts of stem we will presently study. 



86. The direction taken by stems, &c., or their mode of growth, 



