Saturday, January 8, 2011

Doodia caudata, a beautiful Australian with cosmopolitan vocation

Its new fronds of bright red and easy cultivation make it very attractive for gardeners who love the ferns. From Australia, Tasmania, New Zealand, New Caledonia and Lord Howe Island, which is called "small raspfern" has been taken by man to many other places on Earth. In countries of temperate and humid climate similar to their southern land it is grown outdoors as an ornamental. In countries of very dry or cold weather is treated as a houseplant. In nature, living on slightly acidic soils and well drained mainly shaded riparian habitats on the banks of rivers, streams and creeks. Tasmania is ranked in danger of extinction. It needs constant moisture throughout the year. It has become naturalized in the Azores and Madeira.

Beautiful Doodia caudata in cool, moist slopes towards the north of a volcanic mountain (Caldeira do Faial) in the center of the island of Faial in the Azores Archipelago. Its new fronds are very attractive red colour. Grows accompanied by two other alien: left the Australian fern Adiantum hispidulum and right the American Tradescantia fluminensis, the three perfectly adapted to the Azorean climate.

Belongs to the family of Blechnaceae, like the Woodwardia radicans and Blechnum spicant. Its spores are dispersed by wind (anemochory) and, once they have germinated, its prothallus or gametophyte gives rise to a sporophyte or real fern, or by sexual reproduction through fertilization of the female oosphere by a male antherozoids or by apogamy (gametophytic apomixis), growing the sporophyte directly from a somatic cell of the gametophyte bypassing sexual fertilization. It has a short rhizome covered with long light brown scales. Its fronds are dimorphic, the fertile grow upright, stiff and end in a long narrow apex caudate (Latin caudatus caudata, caudatum = with tail), a detail that gives the species name, while the barren, arranged in a basal rosette, are looser and have a pendulum bearing.

Another robust Doodia caudata with upright fertile fronds in early May in the Natural Park of Madeira. To the left is a copy of the fern Anogramma leptophylla. Constant humidity provided by the typical horizontal rain of Macaronesian islands facilitates their survival. (Double click on the photo to enlarge)
It is treated contemptuously as vermin plant, an invasive weed, by become feral very easily and escape from the gardens through the dispersal of spores. She has no guilt. Not voluntarily traveled from the Southern Hemisphere to the Northern Hemisphere, but was brought there by man. Does the same as any other living creature, trying to survive and perpetuate their species on Earth. Evil does not exist in nature, only in the heart of man. The truth is that this is a beautiful fern that grows without forming large populations. Most specimens found in the Azores and Madeira were solitary individuals, not harmed in any other species or competing for territory. In the two photos above and the following is clearly what I mean.

Young specimen surrounded shoots of Tradescantia fluminensis, interspersed with outbreaks of also alien Selaginella kraussiana.

The fertile fronds (the two red) grow very erect, at the beginning of a bright red, which changes to pink and then to green as they mature fronds. Its pinnae are long and narrow and are separated from each other. Can reach 30 cm in length. The sterile fronds (the left) are somewhat shorter,  pinnae are closely spaced and wider than the fertile and the apex is shorter, less caudate.

Frond of Doodia caudata of leathery texture rough touch with finely serrated leaflets, curved spines lined to the tip of the pinnae, hence also called Doodie aspera ssp. caudata. (Double click on the photo to enlarge)

Underside of the apex very long and narrow, caudate, a fertile frond of Doodia caudata with mature sori reach the tip of the tail in early May.

Middle of the previous frond pinnae finely serrated edge, inserted in the rachis with a broad base and sori of slightly more than 1.5 mm each, often confluent and arranged in two rows on each side of midrib of the pinna.

Detail of mature sori of Doodia caudata with indusium slightly raised so sporangia can deliver and disperse spores, which are carried by the wind (anemochory) as far as possible from his mother to conquer new territories. Double clicking on the picture you can see these details, including tiny sporangia hovering below the indusium, which is membranous and lined with small hair.

Sporangium of Doodia caudata seen under a microscope at 400 magnification. (Double click on the photo to enlarge)

And for finish in this microscopic photo spores can be seen with a nice golden brown colour.

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