One often comes across the name of the species as Bulbine mesembryanthemoides, but because Haworth used the spelling mesembryanthoides in his original description, this has to be accepted as correct.
Subspecies mesembryanthoides has a small underground tuber and usually 1-2
leaves (rarely up to 4). The leaves are cylindrical, 1-2.5 cm tall and up to 2 cm in diameter. As soon as the dry summer period arrives, they start to whither.
Flowers appear in spring and summer (Augustus-November), usually after the leaves have retracted. Each plant may have 1-3 inflorescences up to 20 cm tall.
This subspecies occurs widespread from the Knersvlakte in southern Namaqualand to Graaff-Reinet in the Eastern Cape on rocky slopes and flats.
If there were a list of favourite types of succulents, I’m sure the so-called window plants would rank very high. Most of these plants belong to the Aizoaceae (Mesembs), but they are also found in Bulbine and Haworthia.
When one looks up information on window leaves, one gets the impression they are all built on the same principle: the surface of the leaf tip lacks chlorophyll, the central parenchyma* reaches up to the epidermis and as a result of this combination, the leaf tip looks and acts like a window.
In a few cases however, the windows are formed differently.
It has taken me quite a while to find a place where this is described in a comprehensive as well as comprehensible way.
In Cactus & Succulent Journal (US) vol. 16, 1974, Werner Rauh published an article called Window-leaved succulents. He starts his explanation with a description of Haworthia obtusa (=cooperi) var. pilifera and uses more or less the following wording:
“The numerous fleshy leaves are nearly hidden in the substratum and we can only see the transparent, glass-like leaf tips, ending in a long hair. The transparence of the leaf tips is caused by a lack of chloroplasts**. We find the assimilation parenchyma only in the lower two thirds of the blades, but these leaf parts are not accessible to the light. The consequence of this anatomical structure is that light, necessary for assimilation, can reach the assimilation parenchyma only by passing the transparent windows. But the leaves of H. pilifera are not in the morphological sense true window leaves.”
He then moves on to Haworthia obtusa (=cooperi) var. dielsiana, saying:
” … the most remarkable feature is the behaviour of the leaves in the course of their development: young leaves are of the same shape as those of H. pilifera, but becoming older, the upper third of the lamina, which exceeds the soil surface, dies off, so that only the water parenchyma, covered by the shrunken epidermis is to be seen. The lower parts of the leaves with the assimilation parenchyma are hidden in the ground; sunlight can reach it only by passing through the water parenchyma.”
This is the same type of window formation we find in Bulbine mesembryanthoides. In Rauh’s words:
“Becoming older, the upper parts of the leaves die off, as in Haw. obtusa var. dielsiana and the result is the formation of a big window with a plane surface. The assimilating parenchyma is completely hidden in the substratum.”
We know that strong sunlight destroys the chlorophyll, which is essential for the plant’s metabolism. Window-leaved plants are hidden in the ground (at least in the hot and dry season) and sunlight can reach the assimilation tissue only through the windows, passing through the water parenchyma. This filtering process protects the plants against very strong light.
In experiments carried out with Fenestraria, it was found that the light is reduced so much that the chloroplasts will not be damaged, but stays strong enough to allow sufficient assimilation and production of organic substance.
* parenchyma is the relatively undifferentiated tissue that makes up the bulk of many plant organs and is often used for storing of water or food.
** chloroplasts are the tiny parts within plant cells that contains chlorophyll.
This is what the plants look like when the tips of the leaves start dying down.At the end of the process the plants look like this.
With the many warts and teeth on the ends of their leaves, these fascinating plants are always immediately recognizable. They are so unlike other Conophytums that originally they were placed in a genus of their own: Berrrisfordia.
They form tight mats or cushions, with leaves to 1.5 cm long.
The whitish-pink to mauve flowers appear in late winter or early spring; they open in the morning and are scented of raspberries.
The species only occurs on granite domes in the highest part of the Kamiesberg in Namaqualand.
The pictures below are recent scans of slides that I made several years ago. The scanner I used before refuses to work with my current PC, so I decided to buy a new one for converting old slides that still might be put to good use.
After working on a picture for a long time, it often becomes very difficult to keep looking at the results in an objective way.
Therefore I would like to call in your help by letting me know if you think the quality of these pictures is on a par with what you have come to expect in this blog OR is at least good enough for the purpose.
If yes, wonderful; if no, I will just have to further improve my scanning skills!
The first picture -taken in August- shows that not only human beings like these plants. After winter rainfall, they are a juicy bite for hungry animals (in this case probably a tortoise).
The next four pictures were taken in October and November, when progressing heat and drought start discolouring the plants.
After summer the plants may look quite miserable (as shown in the last picture, taken in April).
Both the genus name and the specific epithet are derived from the word gibba (hump, referring to the irregularly swollen leaves).
Plants of this species are sometimes locally abundant in the Western part of the Little Karoo and the Southwest corner of the Great Karoo (Ceres, Laingsburg, Montagu and Worcester), usually in pebbly shale or quartz patches.
They form more or less compact clumps up to 15 cm in diameter with a woody rootstock.
The pink to purple flowers are 2-3 cm in diameter and appear in early spring (August).
Here G. gibbosum is accompanied by Tanquana prismatica (on right)
It takes plants of this species 5-10 years to reach maturity and become columnar.
There are 2 subspecies, each with a number of local forms.
The plants are often locally abundant on gentle slopes and in depressions (often with quartz gravel); sometimes they also occur in shallow soil on rocky outcrops.
The flowers are white, pale yellow (often tinged red) or rarely almost red.
Subsp. columnaris is usually unbranched, with columns 2-3.5 cm wide, often as long as broad.
The inflorescence is swollen, rounded to flat and appears from May to September
The plants are monocarpic, which is another way of saying they die after flowering.
They are found in most parts of the little Karoo, the adjoining western Great Karoo and towards Calvinia. Subsp. prolifera reaches a height of 3-10 cm when in flower and forms several short branches at the base. Often these branches easily break off and take root.
The inflorescence is more or less branched and appears from July to October. After flowering, the plants often regenerate from the lower branches.
This subspecies occurs in most parts of Namaqualand and adjoining areas of Bushmanland and southwestern Namibia.
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.
