DISTRIBUTION OF TRIBES. 477 
the world, especially the extratropical world north and. south, and 
has received a separate name in. almost every country, although 
the distinetive characters given might be generally found in Euro- 
pean specimens. It is so readily carried, however, with cultivation, 
that it is difficult to say how far it is a denizen or a colonist only 
in the distant regions where it is found. 
Sonchus, with about the same number of species (twenty-four) as 
Picris, is similarly cireumstanced as to geographical distribution, 
the chief seat being the Mediterranean region and the Canary 
Islands, with one or two species everywhere accompanying culti- 
vation and possibly true denizens in more than one distant extra- 
tropical region ; but neither the one nor the other has established 
any endemic groups or distinct species beyond the main area of 
the genus. 
Lactuca, sixty species, nearly allied to Sonchus, has a much wider 
range, and is generally moreeastern. It is, however, divisible into 
five or six sections, somewhat different in their geographical distri- 
bution. Brachyrhamphus and Phenixopus belong specially to the 
Mediterranean region. Scariola, containing the typical Lettuces 
of many botanists, is more generally spread over Europe and a 
great part of Asia; Cicerbita and Mulgedium, especially the nu- 
merous and showy blue-flowered species, are frequent in mountain- 
districts, and extend over Europe, central and temperate Asia, and 
N. America, with endemice species in each country.  Zzeris, again, 
is yet more eastern Asiatic, with one European species, and bears 
much the same relation to Lactuca generally which Youngia does 
to Crepis. Chorisma, allied to Zxeris, consists of a few species 
scattered over various parts of Asia, from Asia Minor to Japan. 
Prenanthes, sixteen species, nearly related to the section Cicerbita 
or Mulgedium of Lactuca, has the same range, chiefly mountain- 
ous, over Central Europe, the mountains of Asia and N. America. 
The other genera diverging from Lactuca and Sonchus are limited 
to the northern hemisphere of the Old World. Chondrilla, fifteen 
species, extends over the Mediterranean region and a great part of 
temperate Asia. Picridium, variously estimated at from five to ten 
species, and Microrhynchus, about twenty species, belong to the 
Mediterranean region, the latter extending into north tropical 
Africa and the Canary Islands. Heterachena, one species, is 
Abyssinian and Arabian ; and the monotypic Dianthoseris, allied 
to Lactuca, but with the habit of a Werneria, is limited to the 
mountains of Abyssinia. Five small rather more distinct genera, 
