*1: Newlyn Cliff, 1864,
WC (PNZ) (Paton 1969a:
741).
*2: Elders in old slate
quarry, Trewarmett, N. of Delabole, Apr. 1958, TL (Warburg
1961: 167, Paton 1969a: 741).
Many populations are clearly distinct from var. viridissimus in the
excurrent costa that is thickened towards the leaf apex,
although this character tends to be less developed in young
leaves. However, distinctions between the varieties sometimes
appear subjective because of intermediate forms, in which only
the oldest leaves have thick excurrent costae whereas young
leaves on stems in the same tuft have the costa ending below the leaf
apex. Occurrence of var. stirtonii with many
leaf tips missing was noted several times, so deciduous leaf
tips presumably function as propagules.
Grows as low cushions. Habitat notes from C&S
are as follows. As with the commoner var. viridissimus, recorded
on masonry and as epiphyte, but var. stirtonii differs in
apparently showing a much stronger preference for masonry than
for bark. Recorded mostly from dry base-rich masonry in
unshaded or partly-shaded sites, especially old concrete and
mortar (also on asbestos-cement), on vertical, inclined or
horizontal surfaces, mainly of old walls, also a bridge.
Associates recorded on masonry include Amblystegium serpens
var. serpens, Radula complanata, Scorpiurium
circinatum, Tortula
muralis. A few records from rock substrates include
serpentinite (on the coast and inland), granitic rocks (on
cliff top) and apparently acidic gravestones. Records as
epiphyte include several each from Elder, oak and Sycamore,
three from Ash, and one each from elm and Tilia ×vulgaris.
Associates recorded on bark include Orthotrichum
diaphanum, Zygodon
conoideus. A single unusual record from old tarmac of a
track in coastal heath.
Gemmae invariably present. Nine DTH records cfr,
but capsules often scarce. capsules present 5 (two
capsules);
immature 1, 3, 8, 12 (in 12 with numerous capsules, at
Cold Harbour); dehiscing 6
(single capsule); dehisced 2, 6 (single capsules), 8 (many
capsules, Croft Pascoe).
