The Botany of Iceland - 01.12.1942, Side 22

II. SPECIAL PART
1. Icelandic Groups of Species of the Genus Taraxacum.
Though the characters of the Taraxaca are extraordinarily
persistent, and therefore particularly serviceable in the determination
of the species, it may nevertheless be very difficult, if the number of
species is large, to characterize them exactly in such a way that closely
related species can easily be distinguished from each other. The dif-
ference between two species may be very easily discovered when both
species are observed at the same time, but the difference may be very
hard to describe exactly, so that the individual species will be recognis-
able from the description. However, it tumed out at the examination
of the numerous Icelandic species, partly in the field, partly during
cultivation, that the fruit possesses particularly persistent characters and
therefore is especially useful for the characterization of the species. An
extensive picture-material of the fruits will therefore be a very valuable
aid in future studies, and such a material has, as far as possible, been
provided of all the species mentioned in this treatise (see plate I to X).
The fruits have not only been used in characterizing the species, but
have also, especially the size and colour and the length of the beak,
been partly used for the demarcation of the specific groups; the shape
of the fruit, on the other hand, particularly the form and size of the
pyramid, is not so useful for this purpose, for in a few groups of species
it is rather variable in its form and details, and here the outer habitus
of the plants has been our guide as regards the group, in which the
individual species should be placed.
The Icelandic Taraxacum-spccics can be referred to the following
groups of species erected by H. Dahlstedt:
Erythrosperma .......... 3 species
Ceratophora............. 1 „
Spectabilia .......... 107 „
Vulgaria ............... 5 „
A