Fig.
7.4-1. Transverse section of vascular bundle of
sunflower (Helianthus). This bundle contains tracheary
elements of many different sizes, but they all are large enough that
they are probably vessel elements rather than tracheids. Also, since this is an
angiosperm, tracheids would are not so common. The tracheary elements at the
lower part of the bundle are smaller (known as protoxylem), those at the top are
larger (metaxylem; discussed in Chapter 11 page 117 of Plant Anatomy
[Mauseth]). An important point here is that all these tracheary elements are
much larger than all surrounding cells.