Critical Plants noticed on the Excursion. 405 
The species illustrates very well the danger involved in pushing 
to extremes the theory of endemism in British plants. The plant 
was ignored by continental botanists until quite recently, and was 
regarded as endemic by some British botanists. 
Coleman when describing the plant gave his reasons for believing 
that the CE. phellandrium of Koch was in part the new species ; 
and Coleman’s statement has received justification in Gluck’s 
discovery of CE. fluviatilis in Germany and in Luxembourg. Further, 
Dr. Ostenfeld has this year found the plant in Denmark. The 
indications, therefore, are that, instead of being an endemic species, 
it will prove to be a member of the flora of other Europaean 
countries. I have no doubt that it will be found to occur in other 
parts of Germany—western Germany at least, in Holland, in 
Belgium, and in France ; and I should not be surprised to find that 
it occurs in Switzerland and Austria. The determination of its 
northern, southern, and eastern limits will be an interesting question. 
Will it occur in northern Africa, like Salicornia lignosa, which was 
thought to be endemic in England up to two years ago ? Dillen 
(Joe. cit.), in the first British reference to the plant, cites “ M. 
aquaticuin Matth. Ed. Valgr. in fol. P. ii, p. 484 ; aquaticum 
umbellatum corinndri folio C. B. Pin, 141; aquaticuin foliis coriandii 
Matthioli, J. B., iii, 2, 9.” If these citations are correct, and they 
seem never to have been enquired into, there was no reason at any 
time for regarding CE. fluviatilis as endemic in the British Isles. 
The plant (CE. fluviatilis) prefers running water: its ally (CE. 
aquatica=CE. phellandrium) prefers stagnant water. Its stem is 
fusiform and creeping at the base: that of CE. aquatica remains 
cylindrical to the base. Its aerial leaves have broad, often almost 
overlapping, segments : the corresponding segments of CE. aquatica 
are smaller, narrower, more acute, more deeply cut, and either not 
or scarcely overlapping. Its partial umbels have longer peduncles 
(c. 3 cm.) than CE. aquatica (c. 1 cm.). Its fruits are longer (c. 5 mm.) 
than those of CE. aquatica (c. 3 mm.), and are more compressed 
(c. 1 : 2) than in CE. aquatica (c. 2 : 3). It is frequently a social 
plant, its stems and leaves often floating in an impenetrable tangled 
mass on the surface of small rivers and large drains, whilst CE. 
aquatica in this country usually occurs here and there, in small 
ditches and in other stagnant waters. Both species vary considerably 
both as regards their respective land-forms and water-forms ; and 
some of these have been named by Professor Gluck. Each species 
may perhaps include a number of small locally endemic forms ; but 
