Guest column: Avonia papyracea

                   A contribution by Theo Heijnsdijk

Taxonomy
Avonia used to be a subgenus of Anacampseros, a relatively small genus in the family of purslanes (Portulacaceae).
The species within the genus Anacampseros consist of small to very small shrublets with a more or less thick, sometimes branched stem. The fleshy leaves form a flat rosette or are attached to the stem in a spiral. A typical characteristic are the stipules (lateral outgrowths at the base of the leafstalks). Often these have been reduced to hairs, or they have grown into parchment-like white scales which in some species can completely cover the stem including the real leaves.  In 1994 Gordon Rowley concluded that these species with scale-shaped stipules deserve the status of a separate genus and thus the genus Avonia came into existence. In it he placed 9 species. There are now 12.  The name is probably derived from the Latin ‘Avus’ which means grandfather. It would then refer to the white scales that give the plants an ‘old’ appearance. Rowley placed a few other Anacampseros-like plants in the genus Grahamia. For the genus Anacampseros itself, according to his classification, 15 species remain.
Together, the genera Anacampseros, Avonia and Grahamia form the branch (tribe) Anacampseroteae within the Portulacaceae.
Incidentally, it is doubtful whether the genus Avonia will hold. It is rather unusual in this day and age to base a genus on a similarity in its external appearance. As a rule, characteristics of the flower and seed and even more so the similarities and differences in DNA play the decisive role.

Flower and fruit
What all representatives of the Anacampseroteae have in common is the construction of flower and fruit.  The flowers, which in all species are only open for a few hours in the late afternoon, always have only 2 sepals, which first completely enclose the flower and often curl up after flowering  but remain joined at the tip so that they stay on top of the developing fruit like a cap. This can be seen very well in Avonia quinaria ssp. alstonii (fig.1).  At a certain moment the cap falls off and the seeds are released.


Fig. 1

Furthermore, there are usually 5 (sometimes 4) petals , which are white, pink or carmine. The stamens are white with yellow anthers and very variable in number: from 5 in, for example, Anacampseros comptonii to as much as 80 in A. quinaria (fig. 2).  The white pistil has 3 lobes.  The fruit consists of a kind of veined basket that often has a narrow opening at the top, so that the seeds come out in dribs and drabs as if with a salt-sprinkler as the flower stem bends to the ground and is moved up and down by the wind.

Fig 2.  Avonia quinaria ssp. alstonii has the largest number of stamens of all Anacampseroteae (up to 80).

A. papyracea was chosen as the type species of the genus because of its most pronounced characteristics. The name papyracea (=paper-like) is particularly appropriate because a stem really looks like a little wad of wafer-thin pieces of paper.  The name was given by the German botanist and director of the botanical garden in Königsberg, Ernst Heinrich Friedrich Meyer (1791-1858). The description in accordance with the taxonomic rules followed a bit later and is by the Austrian botanist Eduard Fenzl. It appeared in 1840 in a large article about the Molluginaceae (which at that time still included the Portulacaceae) in ‘Annalen des Wiener Museums der Naturgeschichte’. Hence the designation ‘E. Meyer ex Fenzl as found in botanical literature.

The white scales undoubtedly protect the green leaves underneath them against the bright sunlight. Rowley observed that under humid conditions the scales deflect somewhat from the stem so that there can be a better exchange of gases (oxygen, water vapor) with the environment. Perhaps water can also be absorbed in liquid form.

Like most Avonias, A. papyracea hails from South Africa (Western and Northern Cape). It is fairly common and grows mainly in plains with white quartz stones. But the plant also grows on dark coloured soil, where it is of course much more obvious. Figure 3, a photograph by Coby Keizer, shows a cluster in Goegap Nature Reserve east of Springbok.


Fig. 3

The former director of the Royal Botanic Gardens at Kew, Sir William T. Thiselton–Dyer, pointed out that the white stems bear a certain resemblance to bird droppings. It is not for nothing that the plant is also called ‘gansmis’ (goose dung) in South Africa.  Probably the geese have a different menu there than in Europe, because here the droppings of geese are just as green as the grass they eat.  Thiselton–Dyer suggested that this is a mimicry plant, which in this way tries to prevent it from being seen as a tasty snack.  If that is the case, then it does not seem to be a successful imitation, because another name for the plant is ‘haasieskos’ (Hare food). The same name is also used for A. ustulata and A. filamentosa.  Thiselton-Dyer made his remark in 1906 in an article in the British ‘Annals of Botany’.  At that time, the flower was still completely unknown.  In the same article he mentions that his friend Nicholas Edward Brown, also from Kew, had been growing the plant for many months, but despite daily observation had never seen a flower on it. Yet, suddenly a fruit appeared from between the parchment-like leaves.  He concluded that the flower had to be very small and hidden under the scales had fertilized itself.  A cleistogamous species, in other words.  Later authors also maintain that the flowers do not open. But that’s not true. Sometimes the plant does bloom and the flowers are not small nor do they remain hidden under the scales (Fig. 4).

Fig. 4.  The flower of A. papyracea and a seed pod.

Thiselton-Dyer also reported in the article mentioned above  that the stalk of the ripening fruit continues to grow so that the seeds are scattered at some distance from the mother plant.  This can also be clearly seen in Fig. 4. However, this is not always the case. In Fig. 5 it  can be seen that the 2 fruits hardly appear from between the scales.

Fig. 5. A full seed pod of A. papyracea and an already emptied one. Both only just visible between the scales.

In addition to the usual species which is nowadays referred to as A. papyracea ssp. papyracea, there is also a subspecies: A. papyracea ssp. namaensis. This occurs in the northwestern part of South Africa and in the south of Namibia and is distinguished by the fact that the scales are not smooth-edged but serrated (saw-edged) or toothed and by the seeds that are lumpy. In ssp. papyracea they are more prickly (Fig. 6).

Fig. 6. The seeds of A. papyracea are slightly prickly.

Seed collection is extremely simple. Holding an empty tube or something similar under a ripe fruit and a tap against the fruit are enough.  Immediate sowing gives excellent results. At a temperature of 25 to 30 °C, the seedlings emerge en masse after a week. Only a short time later, the seedlings proceed to develop the papery scales (Fig. 7).

Fig. 7

Fig. 8.  After a year, they are miniature versions of the mature plants.

Cultivation
I grow the plants in standard cactus soil and I also treat them like cacti. This means that they receive water regularly in summer and that I keep them dry in winter.  I try to keep the temperature in my greenhouse around 8 °C in winter, but it sometimes drops to just above freezing point.  According to the literature, even temperatures of 5 degrees below zero are survived.

Apparently, A .papyracea, like A. ustulata, was also used in South Africa as a kind of yeast for baking bread and making beer.  To this end, roots and stems are dried and ground. It is suspected that the plant also contains psychoactive substances, just as, by the way, A.  quinaria. The brew must have been a kind of ‘spacebeer’.

Literature

Browne, P. (1756). The Civil and Natural History of Jamaica. In Three Parts [3]: 234
Fenzl, E. (1840). Monographie der Mollugeneen, Annalen des Wiener Museums der Naturgeschichte, [2]: 295
Marloth, R (1917). Dictionary of The Common Names of Plants, The Specialty Press of South Africa, Ltd. Cape Town
Rowley, G. (1994). Anacampseros and allied genera- A reassessment, Bradleya 12: 105-112
Sims, J. (1811) Anacampseros filamentosa, Curtis’s Botanical Magazine 33: plate 1367
Thiselton-Dyer, W.T.(1906). Morphological Notes, Annals of Botany 20 (2) blz 123-127

Originally published in Succulenta 93: 2014. Translated from Dutch by FN.

 

 

 

 

 

 

 

 

 

Anacampseros telephiastrum (Gemsboksuring)

This could well be the most common Anacampseros, both in the wild and in cultivation. In nature it occurs wide-spread from the Worcester to the Grahamstown area on rocky flats and slopes.
It is a robust species compared to its siblings, forming clumps up to 5 cm tall from a thick, fleshy root-stock.

The leaves are to 3 x 1.8 cm, arranged in rather lax rosettes. They are triangular in cross-section and range from egg-shaped to almost circular when seen from above, with an acute tip and short hairs (shorter than the leaves) at the base.
The relatively stout inflorescence is 5 – 15 cm tall, with 1 – 4 flowers.

After good rains the plants will resemble the one in the first picture.  

Under more stressful conditions the plants turn yellowish/brownish/reddish, so that they are often difficult to find (especially when they grow in crevices like the next three ones).

The dark pink flowers are 3 – 3.5 cm in diameter and open for 1.5 – 3 hours in the late afternoon and only when the sun shines. In dull weather they stay closed and pollinate themselves. Most flowers appear in November-December.

The basket-like fruits have a charm all of their own.sized_anactele2011_11_30#003_lzn

 

Anacampseros comptonii (1)

When you have a first look at the kind of habitat this species is found in, it looks bare and desolate.
The photo below was made in the beginning of April after good rains,  so one would expect a lot of activity going on.  And there is, but the plants growing here are so small, that you have to look properly to see them. Accidentally, the other interesting dwarf succulent growing in this spot near Nieuwoudtville is a Conophytum named after the same person  (Prof R.H. Compton, the second director of the National Botanical Gardens in South Africa). More about that at a later stage.

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The plants grow in very shallow depressions in flat sandstone rocks. After rains, the depressions are filled with water and the little plants are often completely submerged for some time. The following picture was taken in September.

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In the dry period the plants are often almost invisible (the picture below was taken in November). Can you see the little caudexes?

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The last picture gives a better idea of how charming these miniatures are when in flower  (the caudexes are only 1-2 cm in diameter and 1-1.5 cm tall) .

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Anacampseros albidiflora (1)

Plants of this species are found widespread in the Great and Little Karoo on stony slopes, usually sheltered by rocks or bushes. They are columnar and relatively thick, up to 4 cm tall (when not in flower).
The flowers are white to pale pink and appear mainly from October to January.

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Anacampseros arachnoides


It is easy to take this species for granted, even in spite of the cobwebby hairs it is decorated with.
The following is a quote from Gordon Rowley’s booklet ” Anacampseros, Avonia, Grahamia. A grower’s Handbook” :
“This attractive and distinctive species seeds itself freely around the glasshouse and has long been cherished or tolerated in collections of succulents. The abrupt tapering of the leaf to a spiny tip is its most distinctive feature”
This sounds to me like a nice example of damning with faint praise.

When one inspects the plants a bit closer, the beautiful, almost reptile-like surface texture of the leaves is revealed. I must confess that since I have discovered this characteristic, I look at these plants with renewed respect.

 

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Playing with light

Strange though it may sound, up to yesterday I never managed to make a decent picture of a fully open Anacampseros telephiastrum flower.
Yesterday afternoon I went out to Kanonkop (Cannon head), a rocky outcrop overlooking Montagu. Although I did not find what I had hoped to see, there were several other interesting plants, including a lot of flowering  Anacampseros telephiastrums. In fact I have never seen so many plants of this species together in one spot.  The flowers appear in November and December; they only open late afternoon (the pictures were made at about quarter past four).

For the first picture I just made a photo of what was in front of the camera. The result was not really exciting, to put it mildly.
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For the second one I positioned my camera bag in such a way that it shaded the background. Because of the great contrast in light between the  flower and the dark background, the flower was totally overexposed.
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When I took the same picture but with one stop underexposure (and somewhat more close up) the result was as follows.
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This was the basis for the last picture, which was enhanced in post production by lowering contrast and highlights and raising the clarity, combined with a bit of cropping.
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Under cover; ways and means of conserving water

When looking at all those beautiful and unusual forms, colours and textures in succulents, it is easy to think that all this is there  for our enjoyment.  I’m afraid  that is not the case; most of it is purely functional. For me, instead of  being disappointing, this fact adds to my pleasure and admiration.  What can be more likeable than things that are both useful and pleasing to the eye? In this post we will have a look at some of the contraptions that succulents use to conserve water.
The one thing that sets succulents apart from all other plants is their ability to store water that they can use during periods when there is no external supply.  Obviously it is not much use to store a lot of water if you do not have the means to conserve it as well. Managing the stored water sparingly, mainly  has to do with reducing transpiration.
The rate at which plants lose water by transpiration is influenced by a number of factors: size and form of the plant, temperature, humidity, intensity of sunlight, precipitation, wind speed, land slope etc.
On some days the temperature of the soil surface may rise as high as 75 degrees C, but a few centimetres higher up it will usually be much cooler  (up to 40 degrees less ). The two extremes will be separated by a layer of still air.
Comparable layers with gradients of humidity and temperature are found above plant surfaces; they have a great influence on transpiration. These layers are  disturbed or even destroyed by wind.  Because of this, many succulents have a cover of hairs, spines, etc. on the surfaces of their leaves or stems. This helps in producing and protecting these layers.  Such a cover  also gives a certain shade and helps to diminish exposure to strong radiation –especially when it is light in colour.  It has been found that tissue temperatures below spines of the cholla cactus (Opuntia bigelovii) can be reduced by as much as 11 degrees C.

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In this Anacampseros albidiflora, short hairs on the leaves and long bristles between them, cooperate to keep the plant cool

                                                                                                                                                                                                                                                                                                                                Scan75_lznres.jpg
Pelargonium barklyi is a tuberous plant. Although the leaves are short lived, it is apparently worthwhile to protect them with a cover of hairs     


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Haworthia arachnoidea  gets its name from the spiderweb like cover of hairs. This variety is called scabrispina because the hairs are rough and hard like spines

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In Senecio scaposus the leaves look like covered in felt

Many people think that spines are only there to protect the plants against browsing animals.  In line with what we have discussed here, I think that spines play a certain role in that respect too, but that it is not the only, or even the most important, one.

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 In cases like Othonna euphorbioides (above) and Euphorbia stellispina  -and in many other plants- the spines are actually hardened remains of inflorescences

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Leaf and stem surfaces are often thickened too, or coated with a layer of wax (Senecio stapeliiformis, on top) or cork (Othonna herrei)