Abstract
A VERY interesting case of the rapid spread of an introduced species is afforded by Azolla caroliniana, a North American species. So far as the Norfolk Broads are concerned, this free-floating water-fern has hitherto been confined to a single ditch or “dyke” near Horning Ferry, on the river Bure. Here the plant flourished greatly, covering the entire surface, but owing to the isolation of the “dyke” was prevented from spreading. According to an inhabitant of the neighbouring village of Ranworth, the plant has been observed in this one spot for the past fifteen years. I have no evidence as to its original introduction. The disastrous floods of August, 1912, carried some of the plant into the Bure, and its increase during the past twelve months has been extraordinary. Distributed by the tide it is now abundant in several of the Broads, and is carried by the tide in large quantities along the Bure and its tributaries, the Thurne and the Ant. It has found the still waters of South Walsham and Ranworth Broads particularly suited to its needs. It is most partial to the reed swamps of Typha angustifolia, so characteristic of the borders of our fen-lakes, and with this protection it is seen in large crowded expanses. More and more of the marsh and fen “dykes” are being invaded. It seems probable that the spread of the species to the other rivers of the Norfolk system, the Yare and the Waveney, will be prevented by the brackish nature of the water below Acle Bridge. I understand that a hard winter would probably kill the plant off, but its abundant sporocarps would carry it over to the succeeding spring.
Similar content being viewed by others
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
PALMER, W. Azolla in Norfolk . Nature 92, 233 (1913). https://doi.org/10.1038/092233a0
Issue Date:
DOI: https://doi.org/10.1038/092233a0
Comments
By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.