PENTASTICHOUS AND DISTICHOUS ARRANGEMENTS, 151 
or cycle, and thus in the Cherry and Apple the cycle consists of 
five leaves. As the five leaves are equidistant from each other, 
and as the line which connects them passes twice round the stem, 
the distance of one leaf from the other will be 2 of its circum- 
ference. The fraction 2, therefore, is the angular divergence, or 
size of the are interposed between the insertion of two succes- 
sive leaves, or their distance from each other expressed in parts 
of the circumference of the circle, that is 2 of 360°=144° ; the 
numerator indicates the number of turns made in completing the 
cycle, and the denominator the number of leaves contained in it, 
The successive leaves as they are produced on the stem, as we 
have seen, are also arranged in similar cycles. This arrange- 
Fie. 290. Fie. 291. 
Fig. 290. Portion of a branch of the Lime-tree, with four leaves arranged in 
a distichous or two-ranked manner.— Fig. 291. Portion of a branch with 
the base of the leaves of a species of Carex, showing the tristichous or three- 
ranked arrangement. The numbers indicate the successive bases of the 
leaves. 
ment in cycles of five is by far the most common in Dicotyle- 
dons. Itis termed the quincuncial, pentastichous, or five-ranked 
arrangement. . 
A second variety of arrangement in alternate leaves is that 
which is called distichous or two-ranked. Were the second leaf 
is above and directly opposite to the first (fig. 290), and the 
third being in like manner opposite to the second, it is placed 
vertically over the first, and thus completes the cycle, which 
here consists of but two leaves ; the fourth leaf again is over the 
second, and the fifth over the third and first, thus completing a 
second cycle ; and so on with the successive leaves. Here one 
turn completes the spiral, so that the angular divergence is } the 
circumference of a circle, or } of 860°=180°. This arrangement 
is the normal one in all Grasses, and many other Monccotyle- 
dons ; and the Lime-tree (fig. 290), and other Dicotyledons, 
‘exhibit a similar arrangement. 
