Blockeel & Long (1998: 69) treated P. aloides var. minimum (Crome) Mol.
as a synonym of P. aloides, perhaps
following the monograph by Hyvönen (1989). However, records
from Cornwall are treated separately here because it may
represent the interspecific hybrid P. aloides × P. nanum (cf. Timm 1927,
Koppe 1964, Wijk 1956). The circumstantial evidence for some
Cornish plants being this hybrid seems quite strong, in that
both P. aloides and P. nanum are sometimes
present at the same sites, and the var. minimum has
intermediate morphology. However, it is puzzling that spores
of the var. minimum
all appear to be the same size as in typical P. aloides, with no hint
of larger spores (as in P. nanum) or abortive or
variable spores (as might perhaps be expected in a hybrid).
Possibly var. minimum is indeed the
hybrid but has spores of the same size as in typical P. aloides because of
strong maternal effects. Cornish var. minimum also seem very variable,
although this might be attributable to appearance of F2 plants
or even to back-crossing with the parental species.
Records of 'Var. minimum' are as
follows:
12
*1: Trengwainton, 1861, WC
(BM) (Paton 1969a: 710). (Vc1 placed in
brackets because only old records exist: Paton 1969a: 710,
Crundwell 1970: 196).
+1: On stony soil of
steep NE.-facing slope in old mine-spoil, Wheal Busy, E. of
Scorrier, SW74, 1995, DTH 95-385 (BBSUK, DTH)
(Blockeel 1996: 44).
*2: Soil of low bank
beside track in deciduous woodland, N. of Wishworthy, SX38,
1996, DTH 96-381 (BBSUK, DTH) (Blockeel 1997:
41). [Older vc2 report (Roche, in Tellam 1888) not supported
by specimen: Paton 1969a: 710].
Only recorded with well-grown capsules since
non-fertile plants are not reliably separable from P. nanum or P. aloides var. aloides. This form
was probably overlooked in past, or ignored as merely small P. aloides var. aloides. Cornish var.
minimum ranges from
plants intermediate with var. aloides to rare, tiny
plants recalling Tortula truncata
(DTH). Identification as the var. has only
been recorded when several plants together have setae <10
mm.
Mainly found in small amounts, as colonist on
mainly bare acidic soils in sites similar to those of var. aloides, which very
often accompanies it in larger amounts. Recorded in old
china-clay quarries, on earthy mine-spoil, in granitic
quarry-spoil, on hedge-bank, steep soil on part shaded
'hedges' at edge of pastures, beside a woodland track and at
woodland edges, mainly on banks that are commonly N.-facing,
but once on flat ground. Other recorded associates are Nardia scalaris and Pogonatum nanum
(once).
Commonly c.fr.: capsules immature 1, 10; dehiscing
3; dehisced 3, 5, 7.
