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 +====Notes on CYPHOSTEMMA====
 +Text: Andrea Cattabriga. Photos: Ernst J. van Jaarsveld
 +CACTUS & Co. 2 (11) 2007
 +This article aims to contribute to knowl-
 +edge of the genus  Cyphostemma
 +(Planch.) Alston in cultivation, on the
 +basis of my personal experience. It is
 +thus a sort of technical guide dedicated
 +to enthusiasts who cultivate these plants.
 +With regard to taxonomy, I will only indicate
 +some essential points, willingly leaving the de-
 +tails to those who are more familiar with the
 +study of this vast family, that of the Vitaceae;
 +works dealing with this family are available, but
 +not easily.
 +Until about 70 years ago, there was only a single
 +genus, Cissus L., close to Vitis L., which includ-
 +ed the three sections  Eucissus,  Cayratia Juss.
 +and Cyphostemma. Subsequently, Cayratia and
 +Cyphostemma  were elevated to the rank of
 +genus:  Cayratia represents a group of plants
 +with tendrils and no tendency towards succu-
 +lence, whereas the situation is less clear with re-
 +gard to  Cyphostemma  and  Cissus. The distinc-
 +tive characteristic of the former is that of being
 +succulent (caudiciform) and of only growing in
 +the Old World, whereas  Cissus  contains both
 +succulent species (although not strictly caudici-
 +form) and non-succulent species, and its areale
 +also includes the New World. Although the sig-
 +nificance of these characteristics is not such as to
 +justify separation of the two groups, DNA analy-
 +sis appears to show without any doubt that Cis-
 +sus and Cyphostemma are two separate genera,
 +of which Cyphostemma is the branch with most
 +affinity to Vitis.
 +In the florilegium of the plants that have accom-
 +panied mankind’s cultural evolution, the
 +grapevine undoubtedly occupies a prominent
 +place as the generous producer of fragrant
 +grapes, whose fermented juice - wine - has intox-
 +icated us for thousands of years. It may seem
 +strange that this species of sarmentose plants also
 +boasts some relatives, and not particularly distant
 +ones, that are succulents properly speaking, in
 +the ‘caudiciform’ category.
 +The genus Cyphostemma shows some significant
 +similarities with  Vitis, such as the  flowers, very
 +small and collected in racemes, that are similar al-
 +though less numerous and with shorter filaments.
 +The fruits are just like small grapes, with a sharp
 +flavour due to the high tannin content and with a
 +seed twice the size of a grape seed.
 +The leaves are often of the palmate shape of vine
 +leaves, as in C. juttae (Dinter & Gilg) Descoings,
 +but more frequently are profoundly incised and
 +divided into lobes. In some species the succulent
 +tissue present in the leaves makes them thick,
 +compact and leathery. In  C. uter  (Exell & Men-
 +donca) Descoings, C. bainesii (Hook. f.) Descoings and C. humile (N.E. Br.) Desc. ex Wild & R.B.
 +Drumm, the entire leaf epidermis is covered
 +with thin protective hairs, which limit loss of
 +water during transpiration, whereas in C. beti-
 +forme (Chiov.) K. Vollesen, C. currorii (Hook.
 +f.) Descoings and  C. juttae  the epidermis is
 +perfectly smooth and shiny so as to reflect the
 +sunlight efficiently. This latter species, more
 +than the others, is known to secrete a thin
 +pruinous layer that gives the leaves a
 +turquoise colour, sometimes tinged with pink
 +along the leaf-edges in plants grown outdoors
 +in full sunlight. In all the species, the leaves
 +take on a typical conformation in strong sun-
 +light: the lamina curves like a spoon so that
 +the tissue is never directly exposed to inci-
 +dent light.
 +The stem in Cyphostemma species is in absolute
 +the most characteristic and derived organ, with
 +respect to the genus Vitis, from which it is differ-
 +entiated both in that it incorporates succulent tis-
 +sues, but above all for the deciduous nature of
 +the terminal portions. At the end of the season,
 +Cyphostemmas not only lose their leaves, but al-
 +so the terminal stretch of the branches, thin and
 +less well developed.
 +With regard to the shape of the stem, there is a uni-
 +form variation among the various species, which
 +range from climbing plants, still in the form of
 +lianas, such as C. greenwayi Verdcourt, in which
 +the basal caudex has rather reduced development,
 +to the underground tuberous development found
 +in C. humile, entirely given over to the function of
 +accumulating reserves of water and mineral salts.
 +All the other species range between these two ex-
 +tremes: in particular, C. cramerianum already has
 +a succulent basal portion, but still presents long
 +liana-like stems with tendrils, C. juttae and C. uter
 +produce densely-branched stocky stems with a
 +height of 1-2 meters, whereas  C. bainesii  forms
 +conical trunks that do not reach more than 60 cm
 +in height.
 +The ecological form of growth is, as the term sug-
 +gests, the habit of growth that characterises a
 +plant, expressed as an adaptation to the ecologi-
 +cal conditions in which it lives. On the basis of
 +this characteristic it is therefore possible to inter-
 +pret the needs of a specific species.
 +(C. greenwayi)
 +These species are similar to the genera Vitis and
 +Cissus, with a rapidly-growing stem, elongated in-
 +ternodes and the presence of tendrils. The leaves
 +and stem are little succulent or not at all.
 +==Ecology:== these species are adapted to conditions
 +of strong competition with vegetation of the
 +thorny brush type, in which they grow by attach-
 +ing themselves with their tendrils, and using
 +woody bushes and trees as a support, until they
 +reach the ideal condition of light. The climate is
 +characterised by dry winters and rainy summers,
 +with heavy rainfall.
 +==In cultivation:== these plants do not like to be ex-
 +posed to full sunlight or very dry and ventilated
 +conditions. When the substratum is dry the
 +plants rapidly suffer from the lack of water and
 +the leaves and tips of the stems tend to lose
 +turgidity and become flaccid, and growth of the
 +entire plant slows visibly. They have an abun-
 +dant fascicular root system, which requires large
 +containers. The soil should be well-drained and
 +with a good organic content (peat, leaf-mould
 +for 50% -80%).
 +These species are typically  caudiciform, with a
 +conical trunk that it is very wide at the base, with
 +varying degrees of branching. The leaves are suc-
 +culent, leathery, with a trichomatous((Trichomatous = covered with trichomas, hair-like structu consisting of a single epidermis cell growing outwards.))
 +protected by waxy secretions.
 +==Ecology:== these species are adapted to very arid
 +conditions with little competition, and form soli-
 +tary succulent bushes that may be of considerable
 +size, in areas of dry Savannah with seasonal
 +herbaceous plants of small size. 
 +The most xerophytic forms (for example  C.
 +uter) colonise very dry rocky deserts. Their root
 +apparatus consists of short, thick branches
 +whose function is chiefly to provide mechanical
 +support, from which absorbent root hairs grow
 +when rainfall occurs. 
 +The climate is characterised by an intense rainy
 +season, which in the case of the more succulent
 +species may assume an irregular nature, in
 +which intense rainfall alternates with dry peri-
 +ods of varying length.
 +==In cultivation:== these plants prefer hot or very
 +hot positions, exposed to strong sunlight and
 +well ventilated. They require a substratum with
 +a dominant mineral component, well drained.
 +The container must be of good size and depth.
 +Terracotta containers are recommended, with a
 +mulch((Mulch: in agriculture, a layer of material placed on the soil to
 +low evaporation and stop weeds from growing.))
 +consisting of large rock fragments, beneath which the absorbent root hairs can develop.
 +Watering must be such that the substratum
 +dries completely before re-watering. In this
 +sense, particular care must be paid to the
 +species C. uter and C. betiforme, which are the
 +most delicate. In particular  C. betiforme, a
 +species originating from the equatorial deserts
 +of Somalia, is the most thermofilic species, and
 +must be kept in a high temperature including
 +during the winter.
 +The only species considered in this group is  C.
 +humile, which forms enlarged underground
 +stems, like turnips, with buds lying just beneath
 +the surface of the soil.
 +Ecology: technically this type of growth is
 +known as ‘geophytic’, given that the buds in the
 +inactive phase are hidden under the soil. This is
 +an ecological form that provides complete pro-
 +tection against drying by exposure to the sun
 +during the inactive winter phase, from animal
 +predators and from damage due to grass fires.
 +In the rainy season the plant rapidly develops
 +new growth, consisting of deciduous stems with
 +small erect and tomentose leaves. In the same
 +way, growth may be renewed whenever damage
 +occurs that compromises functionality, as in the
 +case of fire, very common in the Savannah zones
 +where this species is widespread.
 +In cultivation: plants of this species are sensitive
 +to water stagnation, but come from areas where
 +there is a good content of organic substance in
 +the soil, deriving from the seasonal grassy cover.
 +The substratum should be of a balanced type,
 +with equal amounts of organic and mineral com-
 +ponents. The container must be at least twice the
 +depth of the height of the napiform stem, which
 +must be kept entirely buried and covered by one
 +or two cm of soil, as in nature. In this case
 +mulching is not necessary.
 +The epidermis of the stem deserves a specific de-
 +scription. In Vitis, as in other woody plants, the
 +growth of the stem causes laceration of the epi-
 +dermis, present only in the young phase, when it
 +collaborates with the leaves in carrying out pho-
 +tosynthesis. After it degenerates the plant pro-
 +duces the rhytidoma, a layer of scales of cork (im-
 +properly called ‘bark’) that protects the underly-
 +ing conducting tissues (the so-called ‘phellogen’).
 +In the  Cyphostemma  species with enlarged
 +stem, on the contrary, a curious character is pre-
 +sent that represents a significant ecological
 +adaptation: the capability to completely renew
 +the epidermis at each vegetative cycle. When the
 +old ‘skin’ is detached in the form of large papery
 +patches, the new epidermis is exposed, green
 +and thus capable of photosynthesis, above all
 +useful in the dry season when the leaves have
 +not yet grown.
 +It should be said that, in this case, the photosyn-
 +thesis function is reduced, given that the stomata
 +that ensure gas exchange are not present, but
 +there are only a few isolated openings, the
 +lenticels. However, these enable in any case ab-
 +sorption of CO2, and thus production of a certain
 +amount of sugar.
 +This particular character, of the epidermis that is
 +continually renewed, is not only present in
 +Cyphostemma, but has evolved in a convergent
 +manner also in succulent species belonging to
 +other families, such as in  Sedum furfuraceum
 +from Mexico and  Tylecodon from South Africa
 +(Crassulaceae), Bursera  and  Commiphora  from
 +Central America and East Africa (Burseraceae),
 +Othonna from South Africa (Asteraceae) and to a
 +lesser extent also in  Oxalis from Chile (Oxali-
 +daceae). It is therefore probable that this is a char-
 +acter that gives a certain advantage in terms of
 +adaptation, possibly connected to the opportuni-
 +ty it gives these plants of carrying out photosyn-
 +thesis even when environmental conditions do
 +not enable the production of leaves.
 +Propagation of the Cyphostemmas is tradition-
 +ally by seed. It is reported that in South Africa
 +they are sown by scattering the seeds onto the
 +ground. The small patch of land is then left in
 +the care of the tropical climate, which causes
 +gradual germination of the seedlings over a
 +number of years (Specks, personal communica-
 +tion). Also in captivity I have noticed that the
 +seeds remain vital up to five years after sowing,
 +so that, when the first seedlings that germinate
 +are repotted, it is good practice to place the soil
 +in which they were sown on the surface of the
 +new pots.
 +The soil I have always used is standard soil for
 +succulents mixed with silicon sand. The seeds
 +should be covered with 2 mm of fine sand. I have
 +always had best results by sowing in mid-summer:
 +it appears that heat aids germination.
 +Propagation through  stem cuttings is also rela-
 +tively simple, but usually the value of our speci-
 +men comes from its age, so that pruning rarely
 +produces cuttings. The need to attempt to save a
 +plant diseased at the base occurs much more fre-
 +quently. In some cases of winter rot I have been
 +able to remove the tips of the branches and keep
 +them dry until summer, when they have rooted
 +and began to grow again normally.
 +H. Jacobsen, A handbook of Succulent Plants, Blandford Press Inc. 1960\\ 
 +G. Rowley, Caudiciform & Pachycaul Succulents, Strawberry Press 1987\\ 
 +SysTax - a Database System for Systematics and Taxonomy, http://www.biologie.uni-ulm.de/systax/index.html\\ 
 +Author’s address\\ 
 +Associazione per la Biodiversità e la sua Conservazione, Via S. Innocenti 35 40138 Bologna
notes_sur_les_cyphostemma.txt · Dernière modification: 2010/06/06 12:40 de alain