Riccardia, GRAY FROM

Reeb, Catherine, Bernard, Elisabeth Lavocat & Gradstein, S. Robbert, 2022, An integrative taxonomic revision of Aneuraceae H. Klinggr. (Marchantiophyta) from Guadeloupe and Martinique, French West Indies, Cryptogamie, Bryologie 20 (8), pp. 135-152 : 138

KEY TO THE ACCEPTED SPECIES OF RiccaRdia GRAY FROM GUADELOUPE AND MARTINIQUE

1. Whole thallus with a conspicuous, whitish border of enlarged, hyaline cells ..... R. schwaneckei (Steph.) Pagán

— Whole thallus not bordered by enlarged, hyaline cells ................................................................................. 2

2. Main axis winged (plants prostrate, delicate. Axis 4-7 cells thick. Branch wings narrower than the costa, margins entire. Surface cells on branches often arranged in oblique rows. Dioicous, rarely paroicous) ......................... ........................................................................................................................ R. regnellii (Ǻngstr.) K.G.Hell

— Main axis not winged .................................................................................................................................. 3

3. Ultimate branches winged. Plants with or without basal stolons .................................................................. 4

— Ultimate branches not or scarcely winged, often curved (when in doubt try both leads). Plants with basal stolons .................................................................................................................... R. stipatiflora (Steph.) Pagán

4. Branch wings as wide as or wider than the midrib, wing cells regularly arranged in a grid-like pattern ......... 5

— Branch wings narrower than the midrib, wings cells not regularly arranged in a grid-like pattern ................ 6

5. Plants robust, to 8-10 cm long, main axis erect or ascending and with a subepidermis, not stolon-like, 2-4-pinnately branched. Wing cells 35-50 µm wide ......................................................... R. fucoidea (Sw.) C.Massal.

— Plants smaller, to 1-2 cm long, main axis prostrate and without subepidermis, stolon-like, palmately branched. Wing cells smaller, 15-30(-35) µm wide ................................................ R. hymenophytoides (Spruce) Meenks

6. Branch wings 2-5 cells wide, surface cells on branches often arranged in oblique rows. Branches often tongue-shaped ............................................................................................................. R. regnellii (Ǻngstr.) K.G.Hell

— Branch wings 1-2(-3) cells wide (lacking in older parts of the thallus), surface cells on branches in straight rows. Branches mostly linear ................................................................................................................................ 7

7. Axis biconvex, very narrow, 0.15-0.25 mm wide, hardly wider than the branches. Dioicous ........................... ............................................................................................................................. R. innovans (Steph.) Pagán

— Axis plano-convex, broader, 0.3-0.7 mm wide, distinctly wider than the branches. Epidemis cells not or scarcely narrower than medullary cells. Monoicous .................................................... R. chamedryfolia (With.) Grolle