Hi Sue,

I don't know the structure of this species but I guess this red ring 
corresponds to a sclerenchym ring (fibers) which means that there is 
lignin. Nevertheless, the presence of suberin is not impossible since 
it can be present (even in xylem) after wounding or depending of the 
'plant strategy' relatively to water exchanges and location in the 
plant or organ...

But it is clear for me there should be sclerenchym fibers to maintain 
the rigidity of the main vain...


But to be certain, you should find someone who knows this species, or 
a description of this species, or try more specific staining for 
lignin (Wiesner's  reagent : Phloroglucinol-HCl, or Maule reaction) 
or Sudan (III or IV) for suberin... on another similar section....


>Hi All;
>I have cross sections of epiphytic platycerium fern fronds stained in
>Alcian Blue -Saffranin O. A thick red ring is apparent around the vascular
>main veins does anyone know how I can distinguish if it is lignin or suberin?
>Have fun
>Ashley
>
>Sue Reilly (Mrs) 
>Histotechnologist
>School of Marine Biology and Aqua Culture
>and School of Zoology and Tropical Ecology
>James Cook University.
>Townsville. Qld. 4811.
>Telephone: 07-47814181
>Facsimile: 07-47251570


-- 
Christian Wuethrich, PhD
Division of Viral Pathogenesis
Beth Israel Deaconess Medical Center
330 Brookline Avenue
Boston, MA 02215
United States