In search of Euphorbia caput-aureum Denis, untraceable since 1910! By Christophe Quénel Fig. 1: Inflorescence of Euphorbia caput-aureum C heered up by the unforeseen rediscovery of Euphorbia biaculeata Denis in November 2013 in southern Madagascar (Quénel, 2014), we, Sébastien Houyelle, amateur botanist from the island of La Réunion, and I decided to start a search for another Euphorbia, discovered and described by the same people in the same period and since then never rediscovered: Euphorbia caput-aureum Denis, the Euphorbia with a golden head(*)! (*) Note: By calling the species “une euphorbe à tête d’or” (here: the Euphorbia with the golden head), Christophe Quénel quotes Marcel Denis (1921) who in its description wrote: “c’est une ­espèce remarquable par sa cyme en glomérule jaune d’or”. Euphorbia World 12(1) 2016 Both being passionate about euphorbias, we had roamed the large island of Madagascar already for a couple of years to take pictures of these beautiful plants in their habitats. They are so countless and very often localized in regions only difficult to access, that we certainly will need several more years to complete this search operation. Therefore, based upon existing documentation and herbarium specimens, we are methodically assembling a photographic collection of every species in situ. But the Euphorbia with the golden head is more like a ghost as it had been discovered and collected on 5 a likewise enigmatic mountain: Mont Mahabenofo, not indicated on any map and absent from all known geographic indices. In brief, a mysterious mountain of which the name could very easily have been written falsely: “mahabenofo” literally stands for “it will yield you a gain in overweight”. That’s an astonishing meaning for a mountain top which, when climbing it, will cause you to lose weight … Later we learned from a Madagascan resident living in the vicinity in fact it is Mont Mahabenofy of which the translation this time signifies: “it will give you many dreams”. So, the Euphorbia with the golden head should grow on a mountain which “gives you many dreams”. Amusing, isn’t it? And without knowing that, we had already dreamt about it … But even if we had known this much earlier, it would not have changed anything: There is neither a Mont Mahabenofy nor a Mont Mahabenofo on the maps! So it took a little bit of a Sherlock Holmes to solve this mystery. I could easily tell you the continuation of our search (for us succulentophiles this quest is of the same value as that for the Holy Grail), but I would have to subtly tell you too where this Mont Mahabenofy is located. Well, by revealing that information, for as long as it would last, it would endanger the permanent existence of this species. So, may the Euphorbia with the golden head once more remain sheltered from any greedy eyes for a couple of years on this mysterious mountain which “gives you many dreams”. At least, while I cannot tell you exactly where we have rediscovered this magnificent Euphorbia, yet I will reveal to you in which way we found it … But firstly let us go a little bit back in time, to ­November 1909! It is in this period that this Euphorbia is discovered by Henry Perrier de la Bâthie. It is collected again a second time in March 1910. Two herbarium specimens have been deposited at Paris (Perrier 10695, Perrier 10647). Finally it is 1921, when the species is described by Marcel Denis in his work Les Euphorbiées des Îles Australes d’Afrique. In 1998, in his Succulent and Xerophytic Plants of Madagascar, Volume 2, Werner Rauh precisely states that the species has never been recollected. In 2004, in the IUCN Red List, the status of the species is more-orless questioned by Thomas Haevermans, who explains (cited verbatim from the IUCN Red List): “The species is very close to other similar species described by W. Rauh (such as Euphorbia iharanae, E. aureoviridiflora, etc.), all very localised. Unfortunately the only collection of E. caput-aureum is located on "Mount Mahabenofo", this locality doesn’t exist anymore and is absent from all the known gazetteers. Further field- Fig. 2: Overview of Mont Mahabenofy 6 Euphorbia World 12(1) 2016 Fig. 3: Euphorbia aureoviridiflora in the Montagne des Français Fig. 4: Stalk of Euphorbia caput-aureum work and taxonomic work is required to ascertain the status of the species and its relationships (synonymy) with closely related taxa”. On July 23rd, 2014, at last we followed in the tracks of Henry Perrier de la Bâthie to find Euphorbia caput-aureum again. Beforehand, we had defined a boundary in which we expected to locate this famous Mont Mahabenofy! We had found the indications on different herbarium vouchers. Then, an in-depth study of the maps of Madagascar did the rest. Two days after leaving Tananarive in a northerly direction, we stopped in a village in the neighbourhood of the marked zone. Two mountains completely surrounded us! There was nothing left but to interrogate the local population. Were we blessed by the gods? Had we done a good job of identification? Doubtless a little bit of the two … Whatever the case may be, we had taken aim correctly: Mont Mahabenofy rose up not far away from us (Figs 2, 3). Before starting to climb it, we wished to know if our plant was there, and if so, at which side. We had taken the precaution to bring along with us a similar plant (Euphorbia iharanae Rauh), that should serve us much better than a lengthy discussion or even as a picture. Now we had to find the right person to talk to, someone capable of going up hill and down the mountains. That’s the part which is the prerogative of Nadia Raheliarisoa, my Madagascan companion, who found our man at first sight! She showed him the plant and he answered her: “Songo-Songo”. So the man knew the plants very well, for it is the Malagasy vernacular name attributed to spiny euphorbias. And when Nadia asked him if he had ever seen the flowers and of which colour they were, he said: “mavo”, which means yellow, and he added that such plants existed on the surrounding mountains. Agreed, we were at the right place! We would have loved to set off at once to verify his assertions, but we had a programme which obliged us to take us a little bit farther on to search for other plants. Therefore we asked him if he could collect a specimen to show it to us on our return. This happened three days later. With beating heart, we saw our man arriving, a Euphorbia in hand, and even more so, it was covered with yellow flowers. It looked like E. aureoviridiflora (Rauh) Rauh (Figs 3, 4), which is located further to the Euphorbia World 12(1) 2016 7 Fig. 5:View of the ridge of rocky chalk and the fragments of dry wood which we explored north in the Montagne des Français, however, it possessed a very different spinescence (Figs 1, 4) and more compact inflorescences, composed of 8-16 subsessile cyathia with cyathophylls of a beautiful yellow colour (Fig. 1). Everything corresponded to the description made by Marcel Denis, so there we held our Euphorbia with the golden head in hand, lost from sight for such a long time. Now we had to look for it in its habitat and we urged our benefactor to help us; of course he accepted to serve as a guide. We thought he would bring us up to Mont Mahabenofy, but finally he took us along a ridge of rocky chalk, very close and at a lower altitude (Fig. 5). On a slope exposed to the north some fragments of dry woodland remained alive, rich in succulent plants and xerophytes (Adenia, Cyphostemma, Uncarina and Commiphora spp.). We found Euphorbia caput-aureum on rocky rises, jostling each other in small pockets containing humus (Fig. 6), accompanied by some aloes and kalanchoes, at the edge of the wood. The species, 8 not very abundant, was regenerating a little bit. We found some juvenile plants (Fig. 7) in the shadow of thickets. According to our guide, more plants exist on Mont Mahabenofy. However, this plant should be cultivated to secure its survival, for its location is often traversed by bush fires. Consequently, today once more the Euphorbia with the golden head may fit in the Malgasy vegetative inheritance; but it remains vulnerable, because its habitat does not seem very extensive. Nevertheless, one day we must climb up to Mont Mahabenofy to verify if it really exists over there, and to get an overview about its quantity. And who knows, maybe other discoveries are to be made on a mountain which “gives you many dreams”. At least, now one knows where it is! References Denis, M. (1921): Euphorbia caput-aureum nov. sp. In: Les Euphorbiées des Îles Australes d’Afrique, Revue Générale de Botanique 34: 105 Euphorbia World 12(1) 2016 Fig. 6: Ramified Euphorbia caput-aureum in full bloom Fig. 7: Juvenile Euphorbia caput-aureum Haevermans, T. (2004): Euphorbia caput-aureum. The IUCN Red List of Threatened Species 2004: e.T44317A10890114. http://dx.doi.org/10.2305/ IUCN.UK.2004.RLTS.T44317A10890114.en. Downloaded on 15 November 2015. Quénel, Chr. (2014): A Euphorbia disappeared for a century! Euphorbia biaculeata. Euphorbia World 10(3): 6-11 Rauh, W. (1998): Succulent and xerophytic plants of Madacascar, Vol. 2: 149. Mill Valley, California, Strawberry Press Text in French by Christophe Quénel, 2015. Translation into English by Pjotr Lawant, courtesy Christophe Quénel. Photos: Nadia Raheliarisoa, Sébastien Houyelle & ­Christophe Quénel; all photos © Christophe Quénel, 2014 Note: For plant lovers Christophe Quénel regularly organises round-trips on Madagascar, particularly visiting the habitat of endemic plants. For that purpose he set up the Tour operator Madabotanik, focussed on the discovery of the Malagasy flora, see the website www.madabotanik.com. For more information contact [email protected]. Author’s address: Christophe Quénel Madabotanik Logt No. 29 Cité des Professeurs Andranovory Antananarivo 101 Madagascar Euphorbia World 12(1) 2016 9