Figs 13–30.

Maryna umbrellata, trophic (13) and cystic (14–30) specimens stained with alcian blue (13–16), iodine (17, 18, 21, 22), acrolein (19, 20), PAS (23–27), and sudan black (28–30). 13 – trophic cells extrude the mucocysts, swelling to a conspicuous envelope; 14, 15 – the periphery appears deeply stained when the focal plane is in cyst centre (14). Squashed cysts (15) show that only the glass layer is stained, while the basal layer and the ectocyst (asterisk) as well as the split mesocyst remain unstained; 16 – when the contents is squeezed out, a spongious mass stains, very likely decayed mucocysts; 17, 18, 21, 22 – iodine stains the glass layer lightly (17; 18, opposed arrowheads; 22) and the contents deeply, especially the “spongy globules” (17, 18, 21) and the plasm between the globules (18, 22, asterisks); 19, 20 – acrolein stains the whole cyst (19), except of the glass granules which appear colourless against the pink background (20, arrows); 23–27 – overviews (23, 24), details from squashed specimens (26, 27), and a sectioned cyst (25) show PAS positive reactions of the basal layer of the pericyst, the endocyst region, and the cyst contents; the endocyst and the basal layer are weakly stained in whole mounts (23, 24). The spongy globules stain lightly (26) but when 4% chromic acid is applied, the plasm between the globules stains rather deeply (27); 28–30 – alcoholic sudan black stains the lipid droplets (28, 29), several of which may unite to larger droplets when the preparation is squeezed (30). BL – basal layer, E – endocyst, G – glass layer, M – mesocyst, MA – macronucleus, SG – spongy globules. Scale bars: 2 μm (Fig. 20), 10 μm (15, 21, 22, 26, 27, 29, 30), 25 μm (13, 14, 17, 24, 25, 28), and 50 μm (16, 18, 19, 23).