Pottia intermedia (Turn.) Fiirn., collected in Grey County, Ontario, is new to the flora of North America. It differs from its closest relative, P. truncata, in its long, cylindric, annulate capsules; its papillose, revolute leaves; and the occurrence of a rudimentary peristome in some plants. Pottia intermedia (Turn.) Fiirnr. occurs generally in Europe, but previous reports for North America are apparently without foundation (Mbnkemeyer 1927). Authorities in Europe differ as to its standing as a species: Warburg (1963) and Jones (1953) give it specific rank while Dixon (1924) considers it a subspecies of P. truncata. This beautiful little moss stands tall for a Pottia species, and the pure patches of it found at Markdale, Ontario, abundantly fertile with their bright red setae and red-bronze capsules, made a surprising and delightful sight on the bare soil. I first found P. intermedia on April 8, 1961, in two locations 25 miles apart in Grey County, the first one mile south of Markdale on Highway 10, the other 3 miles southeast of Shallow Lake, between Owen Sound and Hepworth. In both populations the moss grew on bare patches of light calcareous loam in stubble fields seeded to clover. The capsules were still in good condition (having over-wintered); about one-quarter of them were still immature or had not yet shed their opercula. Associates of the P. intermedia in the above locations were Phascum cuspidatum, Barbula convoluta, B. unguiculata, Ephemerum spinulosum, E. cohaerens, Bryum caespiticium, Pottia davalliana, and P. truncata. At the Markdale site P. intermedia has fruited copiously every year since 1961, in whichever of two adjacent fields was in grass at the time. In another site found in 1965 north of Markdale, the ecology and occurrence of the species were similar. The local scarcity of P. truncata and the abundance of P. davalliana are explained by the calcareous nature of the soil and the high degree of exposure of the sites. Intensive searches for bare-soil mosses in Durham County and spot collecting over much of southern Ontario have shown an almost constant presence of P. davalliana and P. truncata on suitable sites, but no further plants of P. intermedia were found although it is to be expected elsewhere there. Table 1 shows the main differences between P. intermedia, as represented by the Ontario collections, and P. truncata. As in P. truncata, the inflorescence of P. intermedia is autoicous, and capsules mature from late fall to spring depending on weather conditions. The Ontario plants of P. intermedia are tall and robust and easily distinguishable at sight from those of P. truncata. Furthermore, a few plants of P. truncata were occasionally found growing in the middle of dense patches of P. intermedia with both species retaining their 1 Millbrook, Ontario. This content downloaded from 157.55.39.94 on Sat, 19 Nov 2016 04:36:10 UTC All use subject to http://about.jstor.org/terms 236 THE BRYOLOGIST [Volume 69 TABLE 1. A comparison of the main differences between Pottia intermedia, as known from Ontario, and the most closely related species, P. truncata. P. intermedia P. truncata Height of gametophyte 5-7 mm 3-5 mm Seta + deoperculate capsule 9 mm 3-5 mm Empty capsule, length 1.2 mm 0.5 mm Empty capsule, shape Subcylindric, slightly Nearly hemispheric, narrowed at mouth wide-mouthed Annulus One row of broad cells None Leaves, border Revolute three-fourths Plane of length Leaves, papillosity Lightly papillose dorSmooth sally in upper third Peristome Rudimentary one None sometimes present Spores 27-32t _ 23-30O distinctive characteristics. However, of 14 European collections examined, two showed stems and setae as short as those of truncata, two had leaves not papillose or only scarcely so, and two more had spores averaging only 25g,. Proctor (1956) notes that P. intermedia in Cambridgeshire also lacked papillae on the leaf cells. In all these variants the capsules are of the intermedia type: long-cylindrie, with annulus. While many operculate capsules of P. truncata may resemble those of P. intermedia, the capsules of the former immediately widen at the mouth upon removal of the lid while those of the latter retain a form with parallel sides slightly narrowing at the mouth. Regardless of the ultimate disposition of P. intermedia as a species, the local population seems to represent a distinct taxon and is therefore worthy of note. A chromosome count will be helpful in deciding its final status. Duplicates of two of my collections of P. intermedia (1,112 and 1,205) have been sent to the following herbaria: National Museum of Canada, University of Toronto, Queen's University, Duke University, New York. Botanical Garden, U.S. National Herbarium, University of Tennessee, Farlow Herbarium, and the British Bryological Society. They were also distributed through the A.B.S. Moss Exchange in 1963 and 1965.
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Jun 1, 1979
Robert C Ellis 
Open Access