Communications on the adventitious flora, ll

Abstract

Based on the study of herbarium material and living plants, the author completes previous works by reporting the finding of some adventitious Xanthium species.

X. inaequilaterum DC from Southeast Asia is now confirmed for Europe as well.

X. sibiricum Patrin ex Widd., From north to east Asia, has recently been introduced for the first time in Europe (Sweden).

X. pungens Wallr., A species from eastern North America, often confused with X. strumarium L., and until now found adventitiously in Europe, Africa, Australia, and New Zealand, also occurs in eastern Asia (Japan). It seems that this species, in terms of the ease of dissemination, and therefore the damage it can cause to the economy of large areas of southern Africa and eastern Australia, almost equals the famous X. spinosum, L .

X. californicum Greene, a species from the Pacific side of the U.S.A., has been found adventitiously only in southern Australia.

The data for X. ambrosioides Hook. et Arn., for Europe, are partly confirmed and partly completed.

X. argenteum Widd., Incompletely known and proven so far only for the central part of Chile, is registered as new for Europe; Attention is drawn to the dubious X. multifidum Larr.

These last two species, as well as Y. catharticum H. B. K., endemic to the Andes and many times erroneously cited as adventitious for Europe, are recommended to the attention of South American botanists.