The easiest way to 'see' stomata on a leaf is to take a nail varnish impression of it. Paint about 1cm2 of the underside of the leaf with transparent nail varnish. Allow to dry out thoroughly.[It takes about 30mins].Then peel off and place on a microscope slide. The stomata leave clearly visible impressions in the nail varnish.If you use a graticule slide you can count how many stomata are on the leaf. Other technicians report equal success using a thin layer of PVA glue instead of varnish.