BOTANICAL TERMS AND DEFINITIONS. xliii 
Tunic, vide Aril. 
Twining, (Volubilis) stems are so called that by their own spiral 
form twine round other plants. 
Two-edged, (^racfps) applied to stems having two angles, or edges; 
applied also to leaves of the sword-shaped form. 
Umbel, (Umbella) this term is applied to a peculiar form of inflores- 
cence : an umbel consists of several flower stalks or rays, 
nearly equal in length, which spread from one common cen- 
tre, and the summits of which form a regular surface, either 
level, convex, or globular, more rarely concave. When 
each stalk or ray is single flowered, it is called a simple 
umbel ; but when each ray or stalk terminates in another 
set of rays, it is called a compound umbel, and these 
smaller umbels are called Umhdlatee, or partial umbels : 
the carrot, parsley, hemlock, &c. are examples of the com- 
pound umbel. 
Unarmed, (Inerme) applied to the margins of leaves devoid of 
spines or thorns. 
Undulated, {Undulatum) applied to leaves when the margins are 
waved obtusely up and down. 
Unequal, (Inesquale) applied to leaves when the two halves are 
of unequal size. 
United, applied to flowers implies the same as perfect. Fide 
Perfect. 
Utriculus, this term is applied to a species of capsule resembling 
a small bladder, which varies in thickness, never opens by 
valves, and falls with the seed ; this species of pericarpium 
seldom contains more than one seed ; it is more frequently 
called the external coat of the seed, rather than a capsule. 
Vaginant, vide Sheathing. 
Variegated, (Variegatum) this term is applied to leaves when 
marked with white or yellow spots or lines of various 
forms.* 
Veinless, (Avenium) applied to leaves without nerves or veins. 
Y Eim Y, (Venosum) applied to leaves when the vessels which nou- 
rish the leaf are more or less prominent, branched, and 
subdivided, forming a network on one or both surfaces. 
Verrucosus, vide Warty; 
* This variety in the colour of leaves is supposed hy some botanists to be a 
disease. Ed. 
