RELATIVE POSITIONS OF LATERAL MEMBERS, 
appear as radial lines, indicated in Fig. 146 by I-V. Since in this case several 
members stand upon each median plane, thej are arranged in orthostichies ; and 
these again are so placed that they divide the circumference into five equal parts. 
But if the members are considered in reference to their age, as indicated by the 
figures i-ii, it is seen that the divergence between i and 2 is f, as also is that 
between 2 and 3, between 3 and 4, and so on. The divergences are therefore all 
equal, or the members have in this case the constant divergence f. In Fig. 147 
the members are arranged in a quaternary whorl; on each circle or section there 
stand in this case four similar members with the divergence J ; but the successive 
whorls are so placed that the median planes of one whorl exactly bisect the 
angle of divergence of the preceding and following whorls ; the whorls are here 
alternate, and all the members are arranged in eight orthostichies. If, on the other 
Fig. 148. — Diagram of a weakly plant of Euphorbia helioscopia ; c c the cotyledons ; /. / the first, i— lo the later foliag-e- 
leaves ; numbers 6—10 form one whorl; at 5 / in the centre is the terminal flower of the primary shoot, B I J the terminal 
flower of one of the five axillaryshoots, ///, ///, /// the leaves of three axillary shoots of the second order. 
hand, two whorls stand one over the other in such a manner that their members fall 
into the same median planes or cover one another, they are said to be superposed. 
Thus, for instance, the staminal whorl is superposed to that of the corolla in 
Primula ; and in the primary roots of Phaseolus, Tropceolum, Cucurbita^ and other 
Dicotyledons, superposed whorls of lateral roots not unfrequently occur. When 
alternate whorls have only two members, they are said to be decussate, as in Fig. 144, 
a very common arrangement with leaves. 
If it is required to represent by a horizontal projection not merely the diver- 
gences on an axis but those on an axial system, such as a system of leaf-bearing 
shoots, it may be done on the same principle, as is shown in Fig. 148. Each 
