230 PHARMACEUTICAL BOTANY 
The one which is chosen as the starting point is marked and taken 
as 0. 
Other forms of leaf arrangement are: 
Opposite, when a pair of leaves is developed at each node, on 
opposite sides of the stem. Examples: Mints, Lilac. 
Decussate, when the leaves are arranged in pairs successively 
along the stem, at right angles to each other. Example: 
Thoroughwort. 
Whorled or Verticillate, when three or more form a circle about 
the stem. Examples: Canada Lily and Culver’s Root. 
Fascicled or Tufted, when a cluster of leaves is borne from a 
single node, as in the Larch and Pine. 
VERNATION.—Prefoliation or Vernation relates to the way in 
which leaves are disposed in the bud. A study of the individual 
leaf enables us to distinguish 
the following forms. When 
‘ the apex is bent inward toward 
\ \ the base, as in the leaf of the 
a we Tulip Tree, it is said to be 
es inflexed or reclinate vernation; if 
convolute plcate conduplicaté Goybled on the midrib so that 
Fic. 158.—Three principal types of the two halves are brought 
vernation. (Robdbins.) ‘ 
together, as in the Oak or 
Peach, it is conduplicate; when rolled inward from one 
margin to the other, as in the Wild Cherry, it is convolute; when 
rolled from apex to base, as in Ferns, it is circinate; when folded 
or plaited, like a fan, as in Ricinus, Maples, Aralias, etc., it is 
plicate; if rolled inward from each margin toward the midrib on 
the upper side, as the leaves of the Apple or Violet, involute; 
when rolled outward from each margin as Dock or Willow leaves, 
_ revolute. The inner surface is always that which will form the 
upper surface when expanded. 
Lear Venation.—This refers to the arrangement of the veins 
within the leaf. It is dependent upon the course pursued by the 
fibrovascular bundles after they enter the leaf blade. 
The central vein in the leaf is termed the midrib or primary. 
The branches coming off of the midrib are called secondary veins or 
secondaries; those arising from secondary veins are called tertiares. 
