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134
h. weimarck
Summary.
In North Europé two Quercus species occur. Q. Robur L. and Q. petraea (Matt.)
Liebl., and liesides the hybrid between them is known. In Scandinavian and generally
i European literature (except Lasch 18Ö7 and Schwarz 1937) the presence of
stellate hairs ön the under surface of the leaves bas been considered decisive for a
specimen to be classified as Q. petraea or Q. petraea X Robur. This opinion is,
however, not torrect, for the exceedingly polvmorphic Robur-complex has an
eastern race. Q. Robur subsp. puberula (Lasch.) Weim. (Syn. Q. germanicai. puberula
Lasch, Q. Robur subsp. pedunculata var. puberula Schwarz), and this type has the
under surface of the leaves covered by möre or less dense stellate hairs. Q. *puberula
agrees in all other morphological features with Q. * pedunculata DC. and varies in
the same way as the latter type (fig. 1 and T. I). Q. * pedunculata is moreover seldom
absolutely glabrous: at stronger magnification (25—30 X) verv small, simple,
ad-pressed, somewhat crisp hair comp in sight. Q. * puberula is distinguished from
Q. petraea X Robur by its fertility.
Deviating forms within Q. Robur ’pedunculata and *puberula are f.
longi-pedunculata with long and f. brevipedunculata with short female catkins. f. petiolaris
with extcnded petioles and, usualiy, with ± cuneate base of the lamina. f. holophylta
with + entire leaves.
Within Q. petraea some prominent forms occur: f. laciniata with profound
sinuses and acute lobes, f. decipiens within somewhat elongated female catkins.
Q. petraea X Robur was distinguished by Lascii (1857), who described 3 main
types: Q. sub Robori-germanica>Q. Robori-germanica and Q.
subgermanico-Robui . [(>. germanica = Q. Robur L., Q. Robur = Q. petraea (Matt.) Liebl.] The
hybrid is in fact highly polymorphous: this may a.o. be connected with the fact
that it is not quite sterile. The polymorphism is in reality still larger than has been
assumed, f. i. by Lascii (1857) and Ascherson & Graebnf.r (1911). Several of the
forms which liave been referred to Q. petraea and to Q. Robur belong to the hybrid
series. Most oaks with entire leaves, found in North Europé, belong in fact to this
series. They are interpreted as extravagants. The poor ability of fructification, the
sparse pilosity of stellate hairs, the somewhat elongated female catkins and the
varying form of the leaf bases speak in favour of the type being interpreted as a
hybrid. The proper name is Q. petraea X Robur. f. mespilifolia (Wallr.) Weim.
The distribution of the larger units is illustrated by maps (the distribution
in Norway is unforlunalely unknown lo the present author). Q. * puberula is known
from Denmark, Sweden and Finnland an<l increases in frequency from west to easl.
The subspecies is not known from Jylland and is rare along the Swedish west coast.
Q. petraea reaches to south Värmland and south Östergötland in the north, is rare
in Öland and is not found in Gotland nor in Finnland. Q. petraea X Robur has
about the same distribution area as has Q. petraea but reaches in some provinces,
f.i. in north Jylland, northwestern Sjælland. Gotland and Södermanland, outside of
the area of Q. petraea. This condition may be duc to plantation, to distant pollination
of Q. Robur by petraea pollen and (or) lo climatic changes, which have brought ön
a diminished area of Q. petraea, whereas Q. petraea X Robur has been able to
survive (von Post 1933).
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