On the biology of some rice-field weeds in Sardinia : Cotula and Heteranthera

The biology and ecology of Cotula coronopifolia L. (Compositae), Heteranthera rotundifolia (Kunth) Griseb. and Heteranthera reniformis Ruiz & Pavon (Ponte- deriaceae), three new weeds naturalized in rice-fields of central-southern Sardinia, are described. Attention is focussed on the degree of propagation of these "taxa", as a consequence of their suitability for the environmental conditions of Sardinian rice- fields, where it seems that marked convergences exist with regard to the original habitat of these species.peer-reviewe