Fig.
7.2-12a.
Transverse section of grape stem (Vitis). This micrograph shows the bordered pits of an angiosperm in transverse
section. Whereas the bordered pits of pine (Fig. 7.2-11) are
comparatively large and easy to see, those of angiosperms are small and
difficult to see. This is an excellent section (made by Triarch) in which the
wide scalariform pits are actually easy to see (they almost never are as obvious
as this). Each pair of arrows marks the end points of the pits, and the fine
white line located between the arrows is the pit chamber; the pit membrane is
not visible. Being angiosperms, there is no torus stuck to a pit aperture.