Following are photos from sap coming out of cut end of house plant leaf.
Zeiss IM microscope.
No stain.
Andy
x32 objective, Optovar x1 intermediate lens:
x63 objective, Optovar x1 intermediate lens:
x63 objective, Optovar x2 intermediate lens, some sharpening with unsharp mask in GIMP2:
x63 objective, Optovar x2 intermediate lens, further contrast and brightness enhanced in GIMP2: