Imagination can run riot when investigating the microscopic anatomy of algae.
A rather beautiful alga from Western Australia (Cryptonemia species) looks relatively ordinary from the outside—but, when tissues are squashed, expelling the unusual internal cells, a new world of cell shapes is revealed under the microscope.
Cryptonemia sp A99478 habit
Cryptonemia sp A99478 ganglionic cells
What does the image of the large central cell remind you of? It is, in fact, of a ganglioid cell, unique to some members of the family Halymeniaceae. It gets its name because of the resemblance to the shape of a type of nerve cell found in animals, but as far as we know, doesn’t transmit impulses along its long arms as happens with animal ganglionic cells. In fact, the scientific literature is silent on its function.
A similarly unusual cell type from the Kallymeniaceae is the stellate cell.
Kallymenia rubra A35870 habit
Kallymenia rubra A35870 stellate cell
It comes from inside membranous blades, in a similar position to that of ganglioid cells of the Halymeniaceae, and has short, radiating arms. Again, nothing is definitive about its function.
The colourful flowers of Amyema miquelii (box mistletoe), our Plant of the Month for March, 2018, provide an important nectar source for birds and insects at this time of year when few other plants are in flower. It occurs in all Regions of the State with the notable exception of Kangaroo Island (see map on eFloraSA).
Amyema miquelii flowers. Photo J.G. Conran.
Mistletoes are native, woody, hemi-parasitic plants. Their sticky seeds are dispersed by birds and germinate on the branches of trees or shrubs, forming an attachment known as a haustorium that penetrates the wood of their host. They are dependent on the xylem sap of their hosts for water and nutrients but have leaves with chloroplasts to produce their own food by photosynthesis. South Australia has 17 mistletoe species in four genera of the family Loranthaceae. Further information can be found in the 5th edition Flora of South Australia family treatment available here (3 MB pdf).
Mistletoe species vary in their host specificity. Amyema miquelii is usually parasitic on eucalypts (Cormybia & Eucalyptus) and is only rarely found on other genera. Within the eucalypts, it shows a strong preference for box-barked species (such as Eucalyptus microcarpa, grey box, in the Adelaide area), and some smooth-barked gums that are related to the boxes such as E. fasciculosa (pink gum) and E. leucoxylon (SA blue gum), as well as number of mallees mainly from the red mallee group. Its drooping, falcate leaves mimic those of its eucalypt hosts.
Amyema miquelii habit (left, photo: J.G. Conran) and flowers, buds and foliage (right, photo: P.J.Lang).
Amyema pendula is the most similar species to A. miquelii and is sometimes confused with it. Its leaves are of a similar shape but tend to have more obvious parallel venation and a somewhat rusty tomentum. It is most clearly distinguished by the flower clusters which have the middle flower sessile (lacking a stalk). There is very little overlap with A. miquelii in its host preferences. Amyema pendulum is most commonly found on the stringybarks (Eucalyptus arenacea, E. baxteri, E. obliqua), and on selected gum species (E. viminalis, E. camaldulensis, E. ovata), as well as Blackwood Wattle (Acacia melanoxylon).
Amyema pendula flowers (left, photo: P.J.Lang), Mistletoe bird (right, photo: Duncan McCaskill, CC BY 3.0, cropped).
Mistletoes fruit form a principal component of the diet of the mistletoe bird (Dicaeum hirundinaceum), and in turn the bird has evolved to become a major disperser of mistletoe. They have a simple gut that can obtain sugars from the mistletoe fruit and pass it rapidly, avoiding damage to the embryo and leaving the sticky coating relatively intact. Furthermore their specialised perching behaviour helps position the defecated seeds on the host plant branches. Mistletoe birds are widespread across mainland Australia but absent on Kangaroo Island which may account for the lack of mistletoes species there.
Contributed by State Herbarium botanist Peter Lang
Olearia arckaringensis, flower. Photo: A.C. Robinson.
The plant was first discovered in 2000 in gullies of breakaways in an isolated pocket of Arckaringa Station by DEWNR scientists Rob Brandle and Peter Lang. The daisy was recognised to be a new species and described in 2008 by Peter in the Journal of the Adelaide Botanic Gardens (895kb PDF). A further two populations were found in 2011 along the same breakaway system on the neighbouring property, Evelyn Downs. In 2016, O. arckaringensis was listed as Endangered under the federal EPBC Act (80kb PDF).
The recent survey discovered several new population of the species. The search took more than 100 hours and covered more than 100 km of breakaway country. The survey team counted and mapped well over 2000 Arckaringa daisy plants and confirmed that the species is rare with quite specific habitat requirements. It was mainly restricted to breakaway sites that had a softer more powdery underlying substrate and were situated in less exposed areas.
Voucher specimens of Olearia arckaringensis and other plants were collected for the State Herbarium and the Seed Conservation Centre. Such collections are vital to build plant knowledge and improve scientists’ ability to accurately describe and identify different species, whilst the stored seeds are a valuable insure against species extinction.
Olearia arckaringensis, old shrub with woody base. Photo: R. Brandle.
The plant is a small, compact perennial shrub, usually to around 30 cm tall, with grey-green leaves and light violet-lavender flowers (occasionally white) borne on long stalks. It rapidly develops a thick woody base from which it can regrow.
Sometimes, working with algae can be frustrating. Collections come in to the State Herbarium of South Australia from various sources – SA Water, Natural Resource Management groups and Marine Biosecurity, for example. Collecting algae for identification can be a bit of a lottery, however. If essential reproductive stages are missing, and these often can’t be seen by the unaided eye, algal workers at the Herbarium can only provisionally suggest names which is disappointing for both collectors and those attempting the identification. But then, if we are lucky, we can also get samples that are bountifully fruitful, literally smothered in remarkable, although often microscopic, reproductive organs.
Whole plant (left) of Heterosiphonia muelleri and magnified detail (right) of the fluffy appearance. Photo: Bob Baldock.
One such case came from 5 m deep at Cable Hut Bay, near Cape Spencer, southern Yorke Peninsula, collected by James Brook. The alga was dotted with products of sexual reproduction (cystocarps) looking like the fruits of terrestrial plants.
The alga was Heterosiphonia muelleri (Sonder) De Toni in the Dasyaceae, a family named from “dasya” (Greek) meaning “shaggy”, an appropriate description looking in detail at the fluffy branches of this species (see also the Algae Revealed key to common red algae of South Australia, part V, 2.3mb PDF).
Two magnifications of cystocarps, one on a denuded part of the plant, the other with cystocarps nestled amongst threads. Photo: Bob Baldock.
More remarkable than the mass of thin threads covering the plant were the bright orange to red-brown cystocarps. These were stalked, semi-transparent “flasks”, with elegant conical necks through which the spores (carpospores), clustered within, are released to germinate into the next stage of the algal life cycle, an asexual spore plant. Under the microscope they looked “good enough to eat”, but, unfortunately, would not have proved a sumptuous meal, even though numerous.
With such beautifully reproductive material, identification was practically ensured. A look through the microscope showed ranks of large cell alternating with small ones along main branches, characteristic of the family Dasyaceae.
All that remained was to section and stain blue one of the main branches (axes). A central large cell with a ring of 10 small ones, wrapped (corticated) with even smaller ones was present and clinched the identification.
Surface view of a main branch (left) and cross section (right) of the axis of Heterosiphonia muelleri, stained blue and viewed microscopically. Photo: Bob Baldock.
It’s always a pleasure to work with such material, and satisfying when we can be sure of an identification, and I hope this gives you insight into some of the tasks involved in working with algae at the Herbarium.
Contributed by State Herbarium Hon. Associate Bob Baldock.
Scutellinia scutellata, Flinders Chase National Park. Scale bar = 10 mm. Photo: David Catcheside.
A small orange disc fungus, Scutellinia scutellata, is the State Herbarium of South Australia‘s Fungus of the Month for October 2017. This little fungus is widespread, but particularly spectacular in DEWNR’s Park of the Month, Flinders Chase National Park. The common name for Scutellinia scutellata is “eyelash fungus”, because of the long dark hairs fringing the margin of the brilliant orange disc.
Scutellinia scutellata, Flinders Chase National Park, fresh herbarium collection PSC4233. Each division of scale bar = 1 mm. Photo: David Catcheside.
Scutellinia scutellata (L.) Lambotte is a common disc fungus with a worldwide distribution. It is saprotrophic, growing on rotten, wet wood, sometimes on soil but in association with wood. The fruit bodies may be in clusters or gregarious over the wood.
The generic name is derived from the Latin scutum, a shield, with the suffixes -ella, denoting the diminutive stature, and –ineus, meaning resembling. The specific epithet scutellatum means shield or saucer shaped.
The fruit bodies, apothecia, are small, stemless saucers of height 1–5 mm and diameter 2–10 mm, although they may reach a diameter of 20 mm. The apothecia start as tiny spherical knobs which expand and become saucer-shaped. Later the saucers flatten into discs with upturned margins. The surface of the upper disc is bright orange to orange red, its margin is fringed with stiff, bristle-like black-brown hairs to 1.5 mm long. The lower surface is brownish due to the dense brown hairs.
Scutellinia scutellata, hairs on outer surface of apothecium. Scale bar = 10 µm. Photo: Pam Catcheside.