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.