Development of Cassytha filiformis, L. 413 
Stomata are everywhere present and always in great 
abundance. On the leaves they are somewhat scattered, 
elsewhere they are in rows. They are also found on the 
petals, where they are in short rows. They likewise occur 
on the walls of the mature fruit, which represent the per- 
sistent receptacular tube. Cassytha is perhaps unique 
among the Angiosperms in having the stomata placed trans- 
versely to the long axis of the stem. The stomata them- 
selves are rather small and of ordinary appearance. The 
origin of their transverse position, however, is interesting. 
On the hypocotyl, in the colorless and succulent region, they 
are sparse and are placed longitudinally. In the region 
where it attenuates and begins to look green, they are seen 
to lie obliquely and at varying and generally increasing 
angles, until in the green region they lie transversely. Quite 
young stem tips show stomata developing transversely. 
The epidermal cells, which in this region are nearly quad- 
rangular in outline (Fig. 12, a), divide twice in succession, 
both divisions being perpendicular to the long axis of the 
stem. This forms four consecutive cells, which are consider- 
ably broader than they are long, and in cross section decidedly 
deeper than they are long. All four cells have sharply defined 
nuclei and a moderate amount of protoplasm. Fig. 12 b, 
shows this stage. The series of drawings in Fig. 12 is from 
longitudinal sections of the stem, therefore cross sections 
of the stomata. Safranin followed by methyl green causes 
the nuclei to become red or slightly purplish, the cell walls 
and cytoplasm green. It also stains the later thickening of 
the guard cell pink. Of the four cells thus formed the inner 
two are stomatic guard cells, and the further development 
of the stoma is a mere change of shape. The guard cells 
expand, squeezing the outer cells somewhat upward, so that 
they project slightly over the level of neighboring cells, and 
their nuclei are either much flattened, or they settle into the 
lowermost portion of the cell, the greatest pressure being 
upon its middle (Fig. 12, c). 
