Fig.
7.3-3. Transverse section of vascular bundle of
ragweed (Ambrosia). The red band marked by the three arrows is part of a
simple perforation plate, but rather than lying parallel to the plane of
cutting, the plate is tilted upward and the microtome knife
passed right through it cutting most of it away and leaving only this
one piece. The six white dots (three are indicated by arrows) on the rim are
pits. The curved inner edge of the red band is the edge of the perforation
itself.