Normal pinyon pine needle - cross section
Cross section of a normal pinyon pine (Pinus edulis needle.
Round galls and normal needles of the same age were fixed and prepared for sectioning according to the procedures of Sass (1958). After sectioning at 25 um, the material was stained with 1% saffranin-O for 30 min then dehydrated in 95% ethanol and stained with 0.6% acid fast green for 30 sec. Note the resin canal indicated by the circular "bubble" on the right side of the cross-section.

Chemical Ecology