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Dimidiate, halved; as where a leaf or leaflet has only one side developed.

P. 1-2 cm. dimidiate, sessile and fixed by a downy nodule, white, marginate behind, variegated with minute rufescent scales; g. radiating from base, at length brownish rusty; sp. ——. haustellaris, Fr.

P. excentric, generally dimidiate, conchate, elliptical or rounded, mouse-grey then pale, viscid, squamulose; g. deeply decur. base anastomosing, white then tinged yellow; sp. 9-12 � 4-6.

P. convex, dimidiate, sooty, with black squamules; g. decur. distinct, white; s. with black squamules up to sooty ring. dryinus, Pers.

Dimidiate, sessile or with a sublateral stem. scoticus, B. and Br.