Drosera praefolia, buds. Photo: P.J. Lang.

Precocious little early bloomer

The plant of the month for August 2016 is Drosera praefolia, a rare South Australian endemic sundew with the peculiar trait of flowering before its leaves appear.

It is one of an amazing six sundew species found in Onkaparinga River National Park, which is the DEWNR Park of the Month for July. The other sundew species recorded there are the pink-flowered Drosera auriculata (tall sundew), the tiny D. glanduligera (scarlet sundew), D. hookeri (pale sundew), D. macrantha subsp. planchonii (climbing sundew) and D. whittakeri (scented sundew). This is a good time of year to see most of the species. Try the easy 5 km Sundews Ridge Hike or the steeper, more challenging 6 km Sundews River Hike.

Sundews (Drosera spp.) are insectivorous plants bearing stalked glands which produce a sticky mucilaginous material to attract and trap insects. These glandular hairs are responsive to pressure when an insect gets caught and bend in towards it to make further contact. Enzymes are secreted to digest the prey and release nutrients that the plant can absorb. The new treatment of the Flora of South Australia (5th edition) covering all the State’s Drosera species is available here as a pdf file (Conran & Marchant 2011; 3MB PDF).

Drosera praefolia, flowers. Onkaparinga River National Park. Photos: P.J. Lang .

Drosera praefolia resembles the more widespread and common Drosera whittakeri: both species are geophytes with their leaves arranged in a rosette that regrows each year from an underground tuber. Having this underground energy store from the previous season’s growth makes it possible for D. praefolia to flower much earlier and in advance of leaf production. Drosera praefolia flowers April to May and often produces mature seed before its leaves appear, in contrast to D. whittakeri which flowers July to October from fully-formed leaf rosettes.

Drosera praefolia, two typical rosettes. Photo: J.G. Conran.

Evolution of precocious flowering in D. praefolia may have been driven by natural selection to “beat the rush” and catch earlier pollinators in the face of strong competition during winter and spring when conditions are optimal for plant growth and subsequent flowering. Precocious flowering is also a feature of a number of late-summer and autumn flowering lilies, for example Calostemma, as featured in an earlier blog, and Crinum.

Pioneering South Australian botanist and entomologist Johann Gottlieb Otto Tepper described Drosera praefolia in 1892 (in German) drawing on collections and observations he made at Clarendon in the Onkaparinga River Valley ten years earlier while stationed there as a teacher.

Drosera whittakeri. Photo: L.M.B. Heard.

However, D. praefolia was either disregarded or treated merely as an early-flowering variety of D. whittakeri for over a hundred years, until it was reinstated as a species by Bates (1991) (230KB PDF). This is despite its many other differences from D. whittakeri, including smaller flower size, a white (rather than orange) tuber, and leaves with shorter, non-ribbed petioles. For a full account, see the review of the Drosera whittakeri group by Lowrie & Conran (2008) (2.7MB PDF).

Contributed by State Herbarium botanist Peter J. Lang.

Sargassum decurrens. Photo: B. Baldock.

Adelaide shores have recently been battered by high winds and waves, and we generally concentrate on the damage they cause to landscape and property. But storms may also wash in the unusual and unexpected.

A volunteer from North Haven, who works in the State Herbarium of South Australia‘s Phycology Unit, brought in a brown alga, Sargassum decurrens (R.Br. ex Turner) C.Agardh, cast up by the rough weather. Sub-tropical, generally found in Western Australia, Northern Territory and Queensland, this species has only occasionally been found growing in northern Spencer Gulf of South Australia at depths of 6 to 10 m. It’s probably a relict from a time when local seas were warmer, got trapped in the larger of our gulfs when the climate changed and now survives precariously, together with several other sub-tropical species, in areas of high summer temperatures — other relict species include the brown alga Hormophysa triquetra (C.Agardh) Kützing and the red alga Asparagopsis taxiformis (Delile) Trevisan.

How did it get to Adelaide? We have past records of drift plants at Port Stanvac and Marino, but no plants actually attached to rock, so wind and currents presumably have carried them west and north into Gulf St Vincent. Will climate change mean that in the future we might see this species growing on local rocky shores?

Sargassum decurrens, close-up. Photo: B. Baldock.

Sargassum decurrens is dark brown and tough, the main branches are strap-like with characteristic wings, flat-branched and end in thin, “leaves” and gas floats with fine, relatively long stalks. Our specimen is a particularly fine one and will be a welcome addition to the Herbarium’s collections.

Contributed by Hon. Research Associate Bob Baldock.

Sclerotium of Laccocephalum mylittae, dug up in March 2016. Photo: Danielle Calabro.

In late March 2016, Danielle Calabro, a Ranger at Flinders Chase National Park, Kangaroo Island, was digging up Bridal Creeper (Asparagus asparagoides) when she came across a dark brownish-black, monstrous lump approx. 0.5 m underground. Danielle dug it up and contacted Pam Catcheside, Hon. Research Associate at the State Herbarium of South Australia, who works on fungi, to ask if she knew what it was. Pam was able to tell her that it was a sclerotium, a tuber of one of the ‘fire fungi’, Laccocephalum mylittae. Danielle reburied the sclerotium and in late June she, Pam and others (David Catcheside, Flinders University, Helen Vonow, State Herbarium, and Teresa Lebel, National Herbarium of Victoria) who were over in Flinders Chase surveying fungi, went to dig up the fungus.

Sclerotium of Laccocephalum mylittae, held by Danielle Calabro and Pam Catcheside at excavation site, June 2016. Photo: David Catcheside.

Danielle had found the sclerotium in sandy soil under the branches of a fallen Eucalyptus cladocalyx in a disturbed, burnt area of the park. When exhumed, it was found to weigh 7.2 kg and measure 27 × 24 × 19 cm. The interior is white, marbled and solid. It was taken back to Adelaide and dried. Half will return to Flinders Chase, to be put on display at the Flinders Chase visitor centre. The remainder will be kept as an herbarium specimen (PSC 4459, AD-C60004).

Laccocephalum mylittae (Cooke & Massee) Núñez & Ryvarden, native bread, is one of the phoenicoid, the fire fungi, that fruit only after fire. In the case of L. mylittae the mushroom-like fruit body may emerge within a few days after fire.

Native bread is a member of the basidiomycete family, Polyporaceae. The whole fruit body is white to cream, often soil-stained. It consists of a cap which may reach 200 mm diameter, is irregular, flat to dome-shaped, smooth, soft but tough. It has pores, not gills, which are small and rather irregular. The stem is central to slightly off-centre, varies in length and diameter and is tough and solid. It leads down to a sclerotium, an underground tuber which has a dark brown to black skin and a white, marbled interior. Texture is rubbery initially but becomes hard and rather tough. The sclerotia may weigh up to 20 kg.

Site of sclerotium of Laccocephalum mylittae, March 2016. Photo: Danielle Calabro.

Laccocephalum mylittae is a saprotroph, breaking down woody substrates. It is a brown rot fungus, so called because it rots the wood, resulting in a brittle brown cubical mass.

Sclerotium of Laccocephalum mylittae, July 2016. Photo: Bob Baldock.

Fire stimulates the sclerotium to send up a fruit body. This produces spores which, if they land on a damp log, will germinate and form a mycelium, a mat of fine tubes called hyphae. The mycelium proliferates through the log and into the wood, sending the break-down products into the developing sclerotium, rather like the formation of a potato tuber. This sclerotium remains dormant under the soil, sometimes to depths of 0.5 m, until the next fire.

Laccocephalum mylittae produces a true sclerotium, one that is composed of only hyphal matter. Others of the so-called stone fungi, such as L. basilapiloides and L. tumulosum, produce a false sclerotium, one that is mixed with soil and grit.

References

1. Kalotas, A.C. (1996). Aboriginal knowledge and use of fungi. In Orchard, A.E. (Exec. Ed.), Mallett, K. & Grgurinovic C. (Vol. Eds.). Fungi of Australia, Vol. 1B: Introduction-Fungi in the Environment. (Australian Biological Resources Study, Canberra). (Pp. 284-286, as Polyporus mylittae).
2. Robinson, R. (2007). Laccocephalum mylittae – Native Bread. Fungus Factsheet 18 / 2007. (Dept of Environment & Conservation, WA) (500KB pdf).

See also fungi references listed in July’s Plant of the Month blog post.

Contributed by Hon. Research Associate Pam Catcheside.