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STUDIES IN PH LE UM ARENARIUM
365
Dr R. Sterner, Gotlienburg, and Mrs. V. Täckholm-Laurent,
Stockholm, for much help and valuable information regarding the
distribution of the species in question.
2. Taxonomy.
Phlcum (irenarium is a rather unvariable species and the variations
that occur principally concern from a taxonomical point of view
+ useless characters, such as the height of the culm and the relative
lenglh of the panicle compared with that of the culm.
A population from the Cyclades has been described by Vieriiapper
11920, p. 304 ff.; cf. also Bornmüller 1928, p. 326) as ssp. aegaeum.
This form in its typical state differs verv evidently from the general
lype (ssp. eii-arenariiim Hayek) by a number of characters:
ssp. eii-arenarium Hayek ssp. aegaeum Vierh.
Glumes 2.5—3 mm in length. Glumes 2—2.5 mm in length.
Arista 0.4—0.7 mm in length. Keel Arista 0.2—0.5 mm in length. Keel
+ densely ciliate, piles of about sparselv and shortlv ciliate, piles
the same diam. as the ghime. generally < half the diam. of the
Glumella densely and shortlv pilose. glume,
Glumella glabrous or subglabrous.
Vierhapper (I.e.) regarded ssp. aegaeum as a puré geographic
race, endemic in the Cyclades. Låter, however, some collections were
made in Cerigo and Cephalonia too. The elementary requirements for
a geographic race (= subspecies) are (1) the complete substitution of
all other subspecies within the »Rassenkreis» in question in a limited
geographic area, and (2) Ihe occurrence of a border-zone of + fertile
individuals, intermediate between the two forms. The second
circum-stance is very evident in this case. Within the whole easlern part of
the Mediterranean Area Piil. (irenarium shows i obvious transitions
between ssp. eu-arenarium and ssp. aegaeum in wbich the aforesaid
differing characters can be combined in several ways. As has been
mentioned in Post (1933, p. 718), Piil. arenarium v. breviglume
Born-müller, described in 1897 ön material from Jaffa (Bornm. Iter Syr.
No 1606) and which by Vierhapper (I.e.) has been set into connection
with ssp. aegaeum, has nothing to do with Piil. arenarium at all but
is that form which has been commonly called Piil. subulatum v.
cilia-tum (Boiss.) Halaczy. It is distinguished from Piil. arenarium not onlv
by the 5-nerved glumella but also by the size of the anthers ( ± 1.75 mm
in length). The taxonomical range and position of this form will be
dlscussed at a låter occasion.
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