23. Taraxacum sect. Taraxacum
西洋蒲公英组 xi yang pu gong ying zu
Taraxacum officinale F. H. Wiggers, s.l.
Plants medium-sized or robust. Leaves numerous; petiole unwinged or winged; leaf blade usually broad (3-6 cm), deeply lobed to pinnatisect; lateral lobes variously triangular or deltoid, margin usually dentate or lobulate; interlobes evident, often spotted or bordered tan or brownish purple, margin usually dentate. Capitulum 3-7 cm wide. Involucre usually more than 1.2 cm wide, base rounded or flat. Outer phyllaries (12-)15-25(-28), usually mid-green to deep green and sometimes pruinose, variously arranged, broadly linear, linear-lanceolate, or less often lanceolate, usually 12-16 × 2.5-3.5 mm, usually irregularly patent to reflexed, unbordered or with inconspicuous narrow paler borders, apex usually flat but not infrequently callose or sometimes minutely corniculate. Ligules yellow; floret tube glabrous or sparsely arachnoid with variously curved soft thin hairs. Achene grayish straw-colored brown or light olivaceous brown, usually 3-4.5 mm; body densely spinulose in upper 1/4-1/3, ± abruptly narrowing into a conic to subcylindric 0.2-0.9 mm cone; beak usually 0.9-1.3 cm, thin. Pappus white to dirty white, usually 6-7 mm. Sexual or agamospermous.
Numerous species: mostly known from Europe; three (or perhaps more) species (one endemic, two introduced) in China.
Taraxacum sect. Taraxacum in Europe has over 1,000 recognized agamospermous species, but in other continents the knowledge of this section is fragmentary. China has few agamospermous species in this section. One species described from China undoubtedly belongs to T. sect. Taraxacum, and another couple of agamospermous species were identified as T. oblongatum and T. rhodopodum. The low quality of herbarium material and lack of specialized collections do not allow any detailed taxonomic analysis. Taraxacum sect. Taraxacum is represented in China by several species, probably mostly introduced, and their taxonomy requires further study.
The name Taraxacum officinale is generally used to cover the diversity of this section. Until recently, the effective lectotypification restricted the usage of this name to what is most often called T. sect. Crocea M. P. Christiansen, a northern and alpine section. A corrected typification, returning the name to the most common usage (in the sense of T. sect. Ruderalia) was published recently (Kirschner & Štěpánek, Taxon 60: 219. 2011). From now on, the name T. officinale in its broad sense may be used for what is here treated as T. sect. Taraxacum (T. sect. Ruderalia), and the older records under T. officinale usually belong to this section, which is widespread in China.
The type specimen of Taraxacum brassicifolium Kitagawa (Rep. Inst. Sci. Res. Manchoukuo 2: 308. 1938) was not traced. From the description it is obvious that the type plant was an enormously robust "bloated" specimen. The taxon most probably belongs to T. sect. Taraxacum (the only feature not in full accordance with this assumption is the minute corniculation of outer phyllaries, but taxa in T. sect. Taraxacum do not infrequently have this trait). The whitish membranous bractlets on the receptacle margin are treated as a monstrosity. Because of the lack of material and insufficient original description, we do not include the taxon in this treatment.
As the following three species represent a minor fragment of totally unexplored morphological variation and taxonomic complexity of the section in China, we refrain from providing the identification key.