THE STEM 187 
Decumbent, when the stem trails and the apex curves upward. 
Examples: Vines of the Cucurbitacee or 
Gourd family. 
Repent, creeping upon the ground 
and rooting at the nodes, as the 
Strawberry. NOUS Terminal Bud 
STEM ELONGATION.—At the tip of } 
the stem there is found a group of 
very actively dividing cells (primordial 
meristem) which is the growing point 
of the stem. All the tissues of the 
stem are derived from the cells of the 
growing point whose activity gives 
rise in time to three generative regions 
which are from without, inward: 
1. Dermatogen or protoderm forming 
epidermis; 
2. Periblem or ground meristem form- 
ing the cortex, pericycle, and pith. 
3. Plerome or procambium forming 
the fibro-vascular elements. 
DurRaTION OF STEMS. 
Annual, the stem of an herb whose 
life terminates with the season. 
Example: Corn. 
Perennial, when the stem lives for 
many years. Example: Oak. 
Forms oF Stems.—The following 
adjectives appear in pharmacognostic 
and botanical literature in relation 
to the form of stems and in some | 
instances other plant organs: Cylin- }f 
draceous or cylinder-shaped; subcylin- 
drical or somewhat cylinder-shaped; rye. 117.—End portion of a 
terete or circular in cross section; com- branch of the horse-chestnut 
pressed or pressed together above and “Speeg amare te : ee) the 
below or laterally; triquetrous or three- SS 
angled, quadrangular, or four-angled; alate or winged; exfoliating or 
=. 
patee--- Auxillary Bud 
Ce a Leaf Scar 
a Leaf Scar 
ae----- Scars of Terminal 
j Bud Scales 
wy ~~ ~~ 
