Even if one has no knowledge of Latin, it is probably easy to understand that papyracea means papery. This refers to the thin, white scales that cover the stems.
These scales are in fact modified stipules: outgrowths of the base of the leaf stalk. By reflecting and diffusing light, they act as sunshades. This effect, combined with controlled aeration*, reduces evaporation. The scales are also able to trap dew.
*It has been noted that in hot, dry conditions the scales tightly overlap each other like roof tiles, whereas in cooler and therefore damper weather they can open out to some extent so that the leaves are more exposed.
As Gordon Rowley in “Anacampseros, Avonia, Grahamia” (1995) remarks, it seems surprising that such an efficient adaptation has, apparently, evolved only once.
The scales are about 5 mm long and wide and hide the minute leaves.
The stems are usually about 5-8 cm long and 0.7-1 cm thick, arising from a thickened tuber. As in other Avonia species, the stems that carry flower buds grow more or less horizontal, but become erect on the day of flowering and stay that way until the seeds have been dispersed.
The scented flowers are creamy white and appear in late spring and early summer.
There are two subspecies: subsp. papyracea occurs throughout the Little Karoo and is also found in the Great Karoo, whereas subsp. namaensis occurs in southern Namibia, the Richtersveld and Bushmanland. Both subspecies seem to feel most at home amongst white quartz pebbles.
According to the literature the main difference between the two is that in the first one, the edges of the scales are entire (without any teeth or other incisions) and in the second one saw-edged to toothed.
The following pictures show plants of subsp. papyracea.
It may be of interest to see what Prof. Schwantes in his magnum opus Flowering Stones and Mid-Day Flowers (1957) has to say about this “most remarkable and interesting species”: “This forms annually only two pairs of leaves to each growth which, however, are differently shaped. This phenomenon is called dimorphism of the leaf. The pair of leaves that appears at the beginning of the rainy season from out of the dry sheath is united into a long sheath at the base but developed normally above into widely separated, yawning, broad leaf tips. This pair of leaves with its comparatively broad surfaces that catch the light and absorb carbon dioxide as nourishment, provides food during the growth period. When the end of this period approaches there pushes out of the channel formed through the uniting of these normally developed leaves a peculiar, elongated, cylindrical structure which consists of two leaves joined right up to the tip. The very short ends are separated only by a slit, which shows that the growth actually consists of two thick leaves. Growths which consist of such closely united leaves are called plant bodies (corpusculum). The object of this close union can only be to reduce the evaporating surface as much as possible and to protect the young growth within from being dried up. The plant’s struggle to make the leaf pair as nearly spherical as possible is here obvious; as is known, the sphere is the form with the smallest surface area. Within these leaf pairs or plant bodies the next pair develops, which once more is less completely united. Inside the body a channel running its whole length remains open; the slowly developing leaf pair is fitted into this and draws from the plant body food and water until it has dried up to a parchment-like skin which completely surrounds the young pair so that not even the tip projects. In this condition the growth, well protected by the skin, lives through the dry period and when the rains begin the deeply buried pair of leaves quickly emerges from the skin surrounding it. In Ruschia pygmaea quite distinct leaf pairs are produced for the dry and for the rainy seasons, one of which has a large surface for assimilation, while the other serves for the protection of the resting pair.”
23 June 2010
1 Oct. 2006
1 Oct. 2012
29 Jan. 2012
18 Feb. 2007
With its almost furry stems this species is easy to identify, even without flowers.
Only Stapelianthus pilosus from Madagascar is somewhat similar.
The stems are normally 1.5-6 cm long, but may reach as much as 18 cm; they usually have 10-16 spiral or vertical series of tubercles ending in long hairs. These hairs shade the stems and thereby reduce water loss.
The flowers have an unusual appearance too and appear in spring and summer (Dec.-May).
The plants are found sporadically on stony slopes and clayey flats from Montagu eastwards to Steytlerville in the Eastern Cape and in the Great Karoo from Matjiesfontein to Beaufort West. They occur mostly in the shade of low bushes.
Why would a plant like this spend a lot of water and energy to produce succulent leaves, only to let them die back when the dry period arrives?
The only reason I can think of is the following: in winter there is a surplus of water, which the woody underground tuber cannot absorb quickly enough.
Leaves, even succulent ones, can grow much faster than tubers, and therefore can store more water in a shorter period. When the weather starts becoming drier and hotter, the water in the leaves is then gradually absorbed by the tuber.
This recycling of water is best known from the mesemb family. It works a bit differently there (for one, very few Mesembs have tubers) but the general idea seems to me to be the same. For more info on this phenomenon, have a look at Water recycling in succulents.
B. succulenta is often locally abundant in the western part of the Little Karoo and further northwards (Tanqua Karoo and Bokkeveld Mts).
Although the leaves in this species may be up to 13 cm long, they are usually much shorter; the width varies from 0.3-1 cm.
The flowers appear from July through September and are yellow (as in nearly all Bulbines).
Pictures are in chronological order:
1 taken 11 July
2 and 3: 4 Sept.
4: 1 Oct.
The plants form shrubs up to 75 cm tall and seem to prefer stony plains and low ridges. Their thick stems (up to 2 cm thick) have a hard skin containing large quantities of resin and wax. This impervious layer is an excellent way of preventing desiccation.
It also means that the stems can be easily ignited to act as a candle or start a fire.
When you have a good look at the first three pictures, you will notice that the spines start out as leaf stalks, which after a while shed the leaf blades and become hard and rigid.
To be continued.
Succulent plants may store water in any organ of the plant body. Usually, leaves or stems are used for this purpose, but water can also be stored in the roots.
For this reason we speak of leaf, stem and root succulents. In certain plants the distinction is not so clear-cut, because they use more than one organ for water storage. The subject of this post is a case in point.
The first four pictures were made in winter and spring (between mid July and mid October) and clearly show that the species is a leaf succulent.
Or, so it would seem. The last two photos were made in summer (late January). In #5, most of the leaves have disappeared and the plant was only found because the fruits stand out against the background. In #6, the knife points at a plant at either side of it and here too, very little of the leaves is left.
This begs the question how these plants can survive the drought and heat of the remaining summer period. For the answer we have to go beneath the surface (literally). When we do that, we will find a nice fat tuberous rootstock with enough storage capacity for the plants to aestivate (spend the summer in a dormant state).
The species is only found in a small area near Laingsburg, where most of the rainfall occurs in winter.
To give you some idea of the size of the plants: the leaves are up to about 20 mm long, 8 mm wide and 4-4.5 mm thick.
The big bladder cells that cover leaves and calyxes give the impression of beautiful jewellery, but their reason for being there is rather more prosaic. They function as external water storage for the plants (see post 17 Dec. 2012).