Fig. 7.3-4. Transverse section of vascular bundle in parsnip (Pastinaca). This micrograph shows a simple perforation plate lying parallel to the plane of sectioning, but it is in a vessel element with a helical secondary wall rather than a pitted one as in Fig. 7.3-3. The arrow marks the portion of wall that is the perforation plate, the other red bands are helices of secondary wall.

Most of the tissue is slightly out of focus, as is even part of the perforation plate. The perforation lies deep within the section, so by focusing on it, all the rest of the tissue is out of focus. The fact that part of the perforation is in focus and part is not indicates that it is tilted, not perfectly parallel to the plane of sectioning.