30 MOKPIIOLOGY OF STEMS AND BliANCHES. [lESSON G. 



LESSON VI. 



MORPHOLOGY OF STRMS A.\D BRANCHES. 



83. The growth of tlie stem in length, and the formation of 

 branches, have been considered ah-eady. Their growth in thick- 

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

 various forms which they assume will now occupy our attention, — 

 beginning with 



84. The Forms of Stems anil Branches above ground. The principal 



differences as regards size and duration have been mentioned before 

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

 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. 



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

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



Siiff'niticose, when low stems are decidedly woody below, but 

 herbaceous above. 



Frnticose, or shruhhij, 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 caulescen t (that is, to have a 

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

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

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

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

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

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

 Of course leaves an J flowers do not ai-ise from the root. These 

 concealed sorts of stem we will presently study. 



8G. The direction taken by stems, &;c., or their mode of growth, 



