Euphorbia hamata (incl. peltigera)

Hamata means hooked, an apt specific name for this species with its recurved tubercles.

The plants often form dense, much-branched clumps up to about 50 cm tall and 60 cm or more in diameter with a thickened main stem.
The flowers (cyathia really) are surrounded by green or yellowish to red bracts and appear from April to September.
One can find this species from Luederitz in southern Namibia to SE of Worcester in the Western Cape, usually on stony slopes.

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Euphorbia primulifolia (var. primulifolia)

At the end of our latest trip to Madagascar, we stayed in Antsirabe, south of the capital Antananarivo. The area is well known for its succulents and I decided to spend an afternoon in the mountains surrounding the town. For several kilometers the road leading out of town ran through the middle of a wide valley, and what I could see of the mountain slopes did not look promising at all. At a certain moment we decide to take a little side road that seemed to take us out of the valley. This was indeed the case, but even the hillsides appeared to be cultivated.
When the driver asked talked some local people if there were any bare rocks nearby, he got a positive reply, but in spite of their directions no rocks came into view. At a loss what to do now, I decided to just stop at an uncultivated spot and look around.
Picture #1 shows the first plant that I noticed there. Without flowers it could be about anything, but next to it was a group of flowering plants (#2) and immediately the penny dropped.

With a large tuber 10-15 cm long and to 7 cm thick, Euph. primulifolia is a true geophyte. It has a very short stem, hidden in the ground, with a radial rosette of 4-12 leaves. In the dry season the plants are leafless and hidden in the grass; in other words, they are only visible in the rainy season. This growth form allows the plants to survive the yearly grass burning.
The leaves are flat or undulate, 8-11 cm long and 3-4 cm wide.
Usually the plants flower before the leaves appear, but as the pictures show, this was not the case here. The cyatophylls* vary from white or greenish to pink and violet.

This variable species is widespread in the central highlands at about 1400-1500 m in a variety of substrates.

* cyatophylls are the bracts that surround the inflorescence proper in many members of the Euphorbiaceae.

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Plant in cultivation. Scanned slide.

Euphorbia multiclava

This distinctive species forms clumps to 30 cm tall and 40 cm wide by branching dichotomously (an uncommon thing in the genus).
The branches are usually 2-3.5 cm thick and 2-7 cm long, with 10-16 ribs.
The plants grow in the eastern part of Somaliland at altitudes between 1200-1500 m on open  plains where the topsoil is often a layer of powder-like limestone.

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Plant in cultivation; scanned slide

Euphorbia dregeana

As the first picture shows, these up to 2m tall, dense clumps are very conspicuous in the field.
The branches are yellowish-green to grey-green, usually up to 3 cm thick at the base and 1.2 cm in diameter above, with leaves that soon disappear.
Between July to September one can find the plants in flower.

The plants occur mainly in flat open gravelly or sandy plains, sometimes on low stony slopes. They are widely distributed from the Haalenberg east of Luederitz in Namibia to Kamieskroon in Namaqualand and Namies in Bushmanland.

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Euph stapelioides

These peculiar little plants occur in the northwest corner of the Richtersveld (Oranjemund to Koekenaap), where they form rather dense mats.
They have tuberous roots and  tough and fibrous aerial stems, which are more or less terete, 30-100 mm long  and 2-5 mm in diameter. The stems do not stick out more than a few cm above ground, as a result of the continuously blowing sand-blasting winds; they are protected by a thick leathery skin.
The flowers appear from April through September and are usually yellow-green (Williamson in his Richtersveld book gives the colour as mainly chocolate to orange-brown).

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Euphorbia atroflora

Similar to, but taller and more impressive than, E. tescorum, this species occurs in the hilly  region south of Lake Turkana in Kenya on rocky slopes with open bushland between 900 and 1800 m.
The plants grow into sturdy shrubs up to 2.5 m tall, with many 2-3 cm wide branches. These have 4-5, sometimes 6, angles; uniformly green or sometimes with somewhat darker blotches around the spine-shields; slightly constricted every 10-20 cm. The strong spines are to 1 cm long.
The name (with dark flowers) refers to the crimson cyathia; the fruits are almost black.

The pictures were taken about halfway between Baragoi and South Horr on 23 Sept 2015. Altitude about 1440m.
The first picture shows a healthy stand of Euph. magnicapsula ssp. lacertosa in the background.

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Euphorbia tescorum

East Africa harbours several shrubby, spiny Euphorbia species which are often difficult to tell apart.
The species shown here occurs in northern Kenya and adjacent areas in Uganda and Ethiopia in very open bushland (often on lava) at altitudes between 400 and 1500 m.
The plants are mainly branched from the base and are up to 1.5 m(sometimes 2 m) tall. They have branches with 4-8 (usually 5-6)  angles, up to 4 cm thick but somewhat constricted every 10-30 cm, usually with darker markings around the teeth.

Pictures 1 and 3 were taken last September south of Mt. Kulal on the eastern side of Lake Turkana in Kenya. The other two are scans from slides made in 1990 west of the lake.

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