Fig. 3.5-1. Longitudinal section of stem of milkweed (Asclepias). The long, wide cell in the center of the micrograph (marked by arrows) is a sieve tube member, one of the types of conducting parenchyma cells of phloem. Notice that both of its end walls are slightly tilted. This type of parenchyma is covered in more detail in Chapter 8 in Plant Anatomy (Mauseth).