PLANT ORGANS AND ORGANISMS 1 57 
two motions, the circular and the longitudinal, and its most common 
modification is the circle. 
In the alternate arrangement there is but one leaf produced at 
each node. Examples: Aconite, Magnolias. 
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: Thorough wort. 
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. 
The spiral arrangement is said to be two-ranked, when the third 
leaf is over the first, as in all Grasses; three-ranked, when the fourth 
is over the first. Example: Sedges. The five-ranked arrangement 
is the most common, and in this the sixth leaf is directly oyer the 
first, two turns being made around the stem to reach it. Example: 
Cherry, Apple, Peach, Oak and Willow, etc. As the distance be¬ 
tween any two leaves is two-fifths of the circumference of the stem, 
the five-ranked arrangement is expressed by the fraction %. In 
the eight-ranked arrangement the ninth leaf stands over the first, 
and three turns are required 
to reach it, hence the fraction 
% expresses it. Of the series 
of fractions thus obtained, the 
numerator represents the num¬ 
ber of turns to complete a 
cycle, or to reach the leaf conw)ute pllcaU c^duphcate 
which is directly over the first; Pig 8l _ Three principal types of 
the denominator, the number vernation. (Robbins.) 
of perpendicular rows on the 
stem, or the number of leaves, counting along the spiral, from any 
one to the one directly above it. 
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 Tulip Tree, it is said to be 
