MORPHOLOGY OF MEMBERS. 
row. Nodal cells occupying clearly-defined positions produce the leaves in the 
order stated. This development furnishes no evidence that the leaves are formed 
in spiral succession ; the bilateral structure of the stem shows rather that a 
spiral construction is in this case altogether inadmissible. The same may be 
shown to be the case in Marsilea, where the creeping stem bears on its upper 
side two rows of leaves, while the under side forms roots ; the leaves borne on 
the upper side may in this case be united in the order of their age by a zigzag 
Fig. 151. — Diagram of a flower-stalk oi Fritillaria imperialis, showing the divergences of the first twenty-four foliage-leaves ; 
the relative lengths of the internodes are indicated by the larger or smaller distances between the circles. 
line broken right and left, which does not anywhere touch the leafless under side 
of the stem, and corresponds in its course to the bilateral structure of the stem. 
The spiral construction appears also to be meaningless in all those cases where it 
is indifferent whether the spiral be carried right or left. This is the case where the 
members are placed in two rows, with a constant divergence of \, and are thus 
arranged alternately in two orthostichies lying exactly opposite to one another, as is 
the case with the branchings of many thallomes {e.g. Stypocaulon, Fig. 108, p. 139), 
the leaves of Grasses, the lateral shoots of the lime, elm, hazel, &c. In all these 
