50
M I C H A E L L O C K E
(2) the distribution of bundles of fibers, and (3) the expanding cuticulin.
The scale rudiment contains many microtubules arranged longitudinally
which may serve to maintain the overall shape, particularly in the early
stages. The scale cell elongates and flattens. Within and closely pressed
to the plasma membrane, longitudinal bundles of fibers arise with a
characteristic regular spacing, similar to that of the ridges. These bundles
are probably the fibrillar aggregates observed by Picken. Similar bundles
/^ /F\ SVs
x r "Γ \
B
FIG. 15. The formation of the pattern over the surface cuticle. A: Most cuticulin
is deposited in the center of the cell. B : This causes the center to expand in a
hemispherical tubercle. C : Further expansion enlarges the main tubercle, but smaller
ones may arise at the base where increase in area must take place against the
resistance of the cell, as in the formation of the crater-shaped tubercles over the
wax gland.
of fibers (Fig. 9) take part in the formation of bristles in Calpodes
(Locke, 1966a). The bundles of fibers in bristles and scales arise close
to the plasma membrane slightly before the cuticulin and continue to be
deposited as the cuticulin covers the surface. Presumably, the microtubules and the bundles of fibers impose a restraint upon the expanding
cuticulin to determine the shape of the growing cell. The longitudinal
ridges of the scales arise between, or on the opposite side from the
bundles of fibers (Fig. 16). Since the fibers arise first, it is their perio-