Peridium immersed _Endophyllum_. RŒSTELIA, _Reb._ _Peridium_ elongated, at length opening by lateral fissures, or a terminal lacerated mouth. _Spermogonia_ on the opposite surface, on the same or on different leaves. =Rœstelia cancellata=, Reb. PEAR-LEAF RŒSTELIA; spots yellow, then red, prominent; peridia split to the base into laciniæ, which remain united at the apex.—On Pear leaves. Not very common. Autumn. (Plate II. figs. 20, 21.) =Rœstelia cornuta=, Tul. HORN-LIKE RŒSTELIA; spots rusty-brown; peridia cylindrical, slightly curved, yellowish-brown; spores greyish, at length brown.—On the under surface of the leaves of Mountain-Ash. Not common. August. (Plate II. figs. 18, 19.) =Rœstelia lacerata=, Tul. LACERATED RŒSTELIA; peridia clustered in tufts, brown, elongated, splitting to the base in segments; spores light brown.—On the under surface of the leaves, and on the petioles and fruit of the Hawthorn. Not uncommon. May to July. (Plate II. figs. 22, 26.) PERIDERMIUM, _Chev._ _Peridium_ elongated, at length bursting irregularly. _Spermogonia_ scattered, conspicuous. =Peridermium Pini=, Chev.; peridia oblong, scattered, large; spores orange, abundant; spermogonia vernal or autumnal, or both; spermatia large, white.—On leaves and young branches of Scotch Fir. Common in Scotland, occasional in England. Summer. (Plate II. figs. 27, 28.) =Peridermium elatinum=, Lk.; simple, immersed; peridia elliptic, pallid; sporidia orange.—On Silver Fir, altering both foliage and ramification. Not common. ÆCIDIUM, _Pers._ _Peridium_ seldom elongated, opening by a terminal mouth, surrounded by a fringe of recurved teeth, or when short bursting irregularly. _Spores_ disposed in chains. _Spermogonia_ on the same or the opposite surface, clustered or scattered, central or intermixed. SECT. I.—_Peridia scattered_ (_not collected in tufts or clusters_). =Æcidium leucospermum=, DC. WHITE-SPORED CLUSTER-CUPS; spots yellowish; peridia scattered, often covering the whole under surface; spores white, ovate.—On both sides of the leaves of the wood-anemone. Common. June. (Plate I. figs. 4-6.) =Æcidium quadrifidum=, DC. FOUR-LOBED CLUSTER-CUPS; spots brownish; peridia scattered, occupying almost the entire under surface; spores brown, subglobose.—On the under side of leaves of Anemone in gardens. (Lobes at the mouth of the peridium not constantly four.) April to May. =Æcidium albescens=, Grev. MOSCHATEL CLUSTER-CUPS; leaf blistered, whitish, scattered; peridia white, split into a few large teeth; spores yellowish-white.—On leaves and petioles of _Adoxa moschatellina_. Not uncommon. April.