Fig. 11.5-15. Phloem of ragweed (Ambrosia). This micrograph shows the primary phloem fiber cap. This is a relatively large cap, containing many fibers. They are often smaller in other species, even consisting of as few as one or two fibers in any particular transverse section. Although this is a low magnification, you may be able to see a few nuclei and other cell contents at least at this stage, these fibers have remained alive although they have completed the deposition and lignification of their secondary wall.