The Genus Pachypodium
Pachypodium is a genus included in the plant family Apocynaceae. The genus name means thick (pachy) foot (podium) and refers to the thick, almost branchless stems. Members of the Apocynaceae family can have either clear or milkey, white latex, sap as is the case for a relative often associated with Pachypodium, Adenium. On the other hand, Pachypodium always has clear sap.1 Both genre, moreover, are highly poisonness. The first species described by Lindley is Pachypodium tuberosum, which is a synonym for today's Pachypodium succulentum (L.f.) A. DC. Pacypodium are highly collected, esteemed, and cultivated plants by succulent enthusiast's, who depend upon mainly a healthly supply of plants from nurseries. Naturally, regrettably, Pacypodium are collected in the wild--in situ--locations, where such activity, not only for Pachypodium but plants in general theaten, the existense of the species in its natural habitat. Pachypodium namaquanum is an example of such a theartened species.
The genus Pachypodium, according to S.H.J.V Rapanarivo and A. J. M. Leeuwenberg in Pachypodium (Apocynaceae): Taxonomy, Habitats and Cultivation in the Abstract of Taxonomic revision of Pachypodium: Series of Revisions of Apocynaceae XLVIII suggest similar yet minor differences in the taxonomical record of species than what is apparently published in Trees of Southern Africa by A. van Wyk and P. van Wyk. It lists twenty-three species, where eighteen are endemic to Madagascar and five occur in the continental Africa--Angola, Botswana, Mozambique, South Africa, Swaziland and Zimbabwe. In 1999, the publication for Pachypodium (Apocynaceae): Taxonomy, Habitats and Cultivation is the work of several authors: S.H.J.V Rapanarivo, J.J. Lavranos, A.J.M. Leeuwenberg, and W. Röösli: [Hence referenced as Rapanarivo et al.] ("Taxonomic Revision of the genus Pachypodium") S.H.J.V Rapanarivo and A.J.M. Leeuwenberg; ("The habitats of Pachypodium species) S.H.J.V Rapanarivo; AND (Cultivation) W. Röösli) This work, besides any subsequent, relevant journal articles, seems to be the most current "authority" on the genus Pachypodium. Rapanarivo and Leeuwenberg give a better account of the key species to the genus Pachypodium as a whole from other recent literature.
A Brief History of the Genus
The history of the genus begins with Lindley in 1830 as the author of the genus Pachypodium. His taxonomical ranking is based on a single species identified as P. tuberosum (1), which he thought was Echites succulenta (2) L.f., which was identified in 1781. Seemingly, then, the newer genus Pachypodium is acquired from the older genus Echites.
In 1837, on the other hand, G. Don. cited E. succulenta (2) as a taxonomical synonym of the species he identified as P. tomentosum (3). This species of Pachypodium is the only species he readily maintains. So, in the same listing, G. Don. classifies P. glabrum (4) as a species, but labeled it under Echites bispinosa (5) L.f as a basionym, which is a name that has priority over other names later given to the same plant by different authors. That is to say, then, that Echites bispinosa (5) has priority over Pachypodium glabrum (4). Also G. Don. moved to reduce P. tuberosum (1) Lindl. to a synonym of Echites bispinosa (5); a synonym occurs when one of two or more names are used for the same taxon rank of a plant--or, better said, a synonym is a rejected name due to misapplication or difference in taxonomic judgment. Therefore, it would seem, the newer genus Pachypodium under G. Don. takes apparently a lesser priority taxonomically in the ranking of names to the older Echites genus. Both P. tuberosum(1) Lindl. and P. glabrum (4) are reduced taxonomically--one by a basionym and the other by a synonym. Yet, even to G. Don. P. tomentosum (3) remains as a species.
In 1844; however, the Pachypodium genus is redefined. A. de Candolle delineated Pachypodium succulentum (6) based on the apparent earlier taxonomical relationship between the two VALID taxonomical species Echites succulenta (2) AND P. tomentosum (3) G. Don. Moreover, he describes a second species considered to be P. bispinosum (7), even though it has an apparent basionym of E. bispinosum L.f. Furthermore A. de Candolle maintains that P. glabrum G. Don. is a synonym to P. bispinosum (7) [edit: Doesn't P. glabrum (4) G. Don. have less priorty as a name to the identification of Echites bispinosa (5). . . ?]. The last taxonomical move A. de Candolle accepted, according to Rapanarivo et al., is the further delineated P. tuberosum (1) Lindl. into a variety form. He modifies this species by adding the taxonomical rank variety to the species as variety loddigessii (1A). In 1963, Codd cited P. tuberosum var. loddigessii (1A) as a synonym for P. bispinosum(7) A. de Candolle.
Historically the next species were identified by Welwitsch in 1867 and 1871 accordingly P. namaquanum (8) and P. lealii (9); as well as P. saundersii (10) by N.E. Br in 1892. Another well known member (genus) of Apocynaceae is brought to attention as a synonym for P. namaquanum (11) (Wyley ex Harv.). That early citation listed P. namaquanum (Wyley ex Harv.) (11) as Adenium namaquanum (12) Wyley ex Harv. in 1863, an aberrant move considering the obvious morphological differences between Adenium and Pachypodium.
Baker in 1892 contributed the first species accepted into the genus from Madagascar as P. rosulatum (13). Based on Rapanarivo et al.'s work, Madagascar with its more isolated habitats and specialized mico-ecosystems as compared to the broadly defined habitats of mainland Southern Africa will thus become a major source for 'variety' of species in Pachypodium. [See Below Habitats of Pachypodium of Madagascar and Continental Southern Africa'] After Baker, Vatke added P. rutenbergianum (14) in 1885, P. brevicaule (15) Baker in 1887, as well as P. densiflorum (16)--all Madagascar species.
Of importance, Costantin and Bois in 1907 constructed the first, rather, complete treatment of Pachypodium. In their account, Costantin and Bois enumerated seventeen species; where ten were from Madagascar and seven were from Continental Southern Africa. In 1934, however, after another account of the genus by Perrier de la Bâthie, Pachypodium was, according to Rapanarivo et al., distinguished by twenty species with fourteen from Madagascar and six from Continental Southern Africa. Much later, in 1976, Markgraf accepted seventeen species, where twelve derive from Madagascar as the other five come from Continental Africa.
New species have been added since 1976. Lavranos--co-author of Rapanarivo et al.--identified P. inopinatum (17) in 1996 and later in 1997 contributed both P. eburneum (18) and P. bicolor (19) In the reference Pachypodium (Apocynaceae): Taxonomy, Habitats and Cultivation, Rapanarivo et al. in 1999 reviewed the variety rank of many species and revised the speciation of Pachypodium by adjusting (I) P. baronii (20) var. windsorii (21) to P. windsorii (22) AND (II) P. rosulatum (23) var. gracilius (24) to P. gracilius (25). In other words, the aforementioned varieties were raised to species rank. Also P. cactipes (26), which Markgraf in 1976 reduces to a synonym of P. rosulatum (23), Rapanarivo et al. reinstated it as a distinct species.
In the Cactus and Succulent Journal (USA), March-April 2004, Lavranos added a new species from the little visited Makay Mountains in Madagascar. He identified it as P. makayense, with the condition that, despite naming a new species, he held reservations about the use of "infrageneric rank where affinities are not entirely clear (Lavranos, "Summery" p. 75.)" So, in other words, the status of P. makayense is published but not entirely settled. It awaits further reassessment by (I) supplementary, adequate documentation; AND (II) molecular work on infra-generic (species) relationships within the genus Pachypodium as a whole. But for practical reasons; however, Lavranos decided that this taxon should be documented and stated as a species so that the advancement of speciation of Pachypodium can be understood given the taxon's distinct, singular characteristics and geological ___location. P. makayense resembles P. densiflorum "with its thick, irregularly disposed branches" (Lavranos p. 88). Yet P. makayense differs widely from P. densiflorum by its spinescence'--having a spine or spines--and in the form of the flower. It is closest, therefore, to P. gracilius but is distinguished by its heavier branches, its larger flowers, and its white spots at the base of the corolla--the inner whorl of the perianth or collectively all the flower's petals. Geographically the southernmost known locality of P. makayense is 50 km from the northernmost known range of P. gracilius, which grows on sandstone south of the Mangoky River. This distance is characterized by a geologically ancient and deep depression of the Mangoky River. (Paragraph: Lavranos, p. 88)
Lastly it should be noted that there often exists a disparity between scientific, botanical accounts versus cultivated, horticultural assessments in succulent nurseries and between passionate collectors of the genus Pachypodium--as well as other esteemed plants. It would seem that the science of botany is guided by finding, or not finding, meaningful generalizations between taxon constituted a generic--inter-species--speciation concept. Nurseries, on the other hand, are often guided by finding any possible difference that (I) once was so named--possibly--(synonym) OR (II) is now presumed to be a new species (n. n.). This attention to characteristics of a taxon that are deemed not botanically reducible by horticulturalists makes for a vast array sensitive to the slightest difference in species; even if these differences have been demonstrated as having no taxonomical significance or have been reduced to synonymy by botanists. Several debates between scientific botanists, market-orientated horticulturalists, and interested collectors exist over taxon. Recently they are as follows for Pachypodium:
(I) The reduction of P. ramosum Costantin and Bois or P. lamerei var. ramosum (Costantin and Bois) Pichon to P. lamerei Drake, where P. ramosum branches considerably more than P. lamerei Drake;
(II) The reduction of P. menabeum Leandri to P. lamerei Drake, where P. menabeum Leandri is significantly different than P. lamerei Drake in morphology;
(III) The exclusion or synonymy of P. rosulatum var. drakei (Costantin and Bois) Markgr. or P. drakei Costantin and Bois to P. rosulatum Baker;
(IV) The exclusion or synonymy of P. brevicalyx (H. Perrier) Pichon or P. densiflorum var. brevicalyx H. Perrier to P. densiflorum Baker
(V) The species rank of P. griquense L. Bolus when reduced to P. succulentum (L.f.) A. DC.
1 Correction. Earilier it was writtten: "As other members of the Apocynaceae family, Pachypodium possess a milky latex, rich in alkaloids, which, in the case of P. lealii (bottle tree), can be very poisonous." Its correction needs public recognition given that this error has occurred on both articles (I) Pachypodium AND (II) Apocynaceae. According to Rapanarivo et al this statement is inaccurate. As Rapanarivo et al writes in Pachypodium (Apocynaceae): Taxonomy, Habitats and Cultivation, ". . . Adenium species have either clear sap or white latex. Pachypodium has . . . always clear sap." (Rapanarivo et al, p. 5)
Species
(01) P. ambongense Poiss. [Madagascar]
(02) P. baronii Costantin and Bois [Madagascar]
(03) P. bicolor Lavranos and Rapanarivo [Madagascar]
(04) P. bispinosum (L.f.) A. DC. [Southern Continental Africa]
(xx) P. brevicalyx (H. Perrier) Pichon or P. densiflorum var. brevicalyx H. Perrier >>>Rapanarivo et al. synonymy for P. densiflorum Baker
(05) P. brevicaule Baker [Madagascar]
(06) P. cactipes K. Schum [Madagascar] >>>According to Rapanarivo et al. no longer a synonym for P. rosulatum
(07) P. decaryi Poiss. [Madagascar]
(08) P. densiflorum Baker [Madagascar]
(09) P. eburneum Lavranos and Rapanarivo [Madagascar]
(10) P. geayi Costantin and Bois [Madagascar]
(11) P. gracilius (H. Perrier) Rapanarivo [Madagascar]
(12) P. horombense Poiss. [Madagascar]
(13) P. inopinatum Lavranos [Madagascar]
(14) P. lamerei (Madagascar palm) Drake [Madagascar]
(15) P. lealii (Bottle tree) Welw. [Southern Continental Africa]
(16) P. makayense Lavranos [Madagascar]
(17) P. meridionale (H. Perrier) Pichon [Madagascar]
(18) P. namaquanum (Cobas tree) (Wyley ex Harv.) Welw.[Southern Continental Africa]
(xx) P. ramosum >>> Rapanarivo et al. is a synonym for P. lamerei
(19) P. rosulatum Baker [Madagascar]
(20) P. rutenbergianum Vatke [Madagascar]
(21) P. saundersii N.E. Br. >>> Rapanarivo et al. no longer a variety of P. lealii. [Southern Continental Africa]
(22) P. sofiense (Poiss.) H. Perrier [Madagascar]
(23) P. succulentum (L.f.) A. DC. [Southern Continental Africa]
(24) P. windsorii Poiss. [Madagascar]
==Invalid Species or Variety Names:== According to Rapanarivo et al. 1999
Pachypodium brevicalyx (H. Perrier) Pichon >>> P. densiflorum Baker
P. densiflorum var. brevicalyx H. Perrier >>> P. densiflorum Baker
P. champenoisianum Boiteau >>>P. lamerei Drake
P. drakei Costantin and Bois >>> P. rosulatum Baker
P. giganteum Engl. >>> P. lealii Welw.
P. glabrum G. Don >>> P. bispinosum (L.f.) A. DC.
P. griquense L. Bolus >>> P. succulentum (L.f.) A. DC.
P. jasminiflorum L. Bolus >>> P. succulentum (L.f.) A. DC.
P. lamerei var. ramosum (Costantin and Bois) Pichon >>> P. lamerei Drake
P. lealii subsp. saundersii (N.E. Br) G.D. Rowley >>> P. saundersii N.E. Br
P. menabeum Leandri >>> P. lamerei Drake
P. obesum G. Don ex A. DC. >>> Adenium obesum Roem. and Schult.
P. ramosum Costantin and Bois >>> P. lamerei Drake
P. x rauhii Halda >>> P. densiflorum Baker
P. rosulatum var. delphinense H. Perrier >>> P. cactipes K. Schum.
P. rosulatum var. drakei (Costantin and Bois) Markgr. >>> P. rosulatum Baker
P. rosulatum var. eburneum (Lavranos and Rapanarivo) G.D. Rowley >>> P. eburneum Lavranos and Rapanarivo
P. rosulatum var. gracilius H. Perrier >>> P. gracilius (H. Perrier) Rapanarivo
P. rosulatum var. horombense (Poiss.) G.D. Rowley >>> P. horombense Poiss.
P. rosulatum var. inopinatum (Lavranos) G.D. Rowley >>> P. inopinatum Lavranos
P. rosulatum var. rosulatum frma. bicolor (Lavranos and Rapanarivo) G.D. Rowley >>> P. bicolor Lavranos and Rapanarivo
P. rosulatum var. stenanthum Costantin and Bois >>> P. cactipes K. Schum.
P. rutenbergianum var. lamerei (Drake) Poiss. >>> P. lamerei Drake
P. rutenbergainum var. meridionale H. Perrier >>> P. meridionale (H. Perrier) Pichon
P. rutenbergainum var. perrieri Poiss. >>> P. sofiense (Pois.) H. Perrier
P. rutenbergainum var. sofiense Poiss. >>> P. sofiense (Pois.) H. Perrier
P. tomentosum G. Don >>> P. succulentum (L.f.) A. DC.
P. tuberosum Lindl >>> P. succulentum (L.f.) A. DC.
P. tuberosum var. loddigessii A. DC. >>> P. bispinosum (L.f.) A. DC.
P. tuberosum Lodd. >>> P. bispinosum (L.f.) A. DC.
Unknown Species Listing of Names
University of Arizona
(Had to Use Google Cache Page of P. menabeum to Obtain this List of other unknown Pachypodium.)
Links on web page do not offer information about stated species.
Pachypodium integrifolium ???
P. laciniatum ???
P. linearifolium ???
P. sagittatum ????
Uhlig Kakteen Nursery (Germany)
Pachypodium fiherenense sp. nov.; Tulear, Madagascar ???
>>> A speculative explantion for this unknown and little used name, even though the taxon in question is considered a "sp. nov.," is that the unknown author has confused plants in the Apocynaceae' with a species listed by the repected Gordon D. Rowley as in the Didiereaceae family, also a thorny stemed tree collective of plants. With in the Didiereaceae, Rowley states that a Genus/Species exists by the name of Alluaudiopsis fiherensis. Remember that the unknown taxon is entitled Pachypodium fiherense. Fiferensis might have beentransformed into fiherense. Moreover both the Alluaudiopsis genus and the Pachypodium
==Morphology==
(Taken from Rapanarivo et al.)
Habit
Pachypodium species radically vary in habit, whereby "habit" means the plant's physical characteristics, appearances, form, or manner of growth. Pachypodium species have varying forms Bottle-, Cigar-, or Candelabrum-shaped trees with thick branches to diminutive plants with one species having an extremely short trunk. This species, P. brevicaule, has a trunk not over 8 cm but is juxtaposition oddly enough with a grotesque, unnatural looking 40 cm diameter. Most of the species are shrubs not over 4 m high. Nevertheless, P. geayi, P. lamerei, P. lealii, P. meridionale, and P. sofiense take on the habit of a tree about 5 m high. P. rutenbergainum can even reach a height of 12 m. P. namaquanum takes on the height of a tree but branches rarely. All species, except P. decaryi which can be spineless, are thorny at least on the branchlets.
Bark
The bark on Pachypodium species vary from a pale grey to a dark brown or a green-grey that is often smooth. In section the bark of Pachypodium species tends to average about 6 mm thick and is usually colored medium green.
Wood
Pachypodium wood is soft and cream colored.
Spines
Pachypodium form stipules transformed into spines. A stipule is one of a pair of lateral outgrowths at the base of the petiole, the stalk of the leaf, in some plants. All African species and P. geayi as well as P. lamerei have three spines; where two spines together are subequal, while the third is smaller and placed in-between them. All other species have just two paired spines, where the length varies from 1 mm in P. decaryi and P. sofiense to 75 mm in P. namaquanum.
Leaves
Pachypodium leaves are alternate. They can be sessile or petiolate: where sessile means lacking a stem, petiole, peduncle or pedicel; AND petiolate entails having a petiole, which is like a petal, colored and enlarged. The petiole is either densely pubescent--hairy--to glabrous--smooth. The leaves are typically confined to the apices of branchlets, branches, or trunk. The blade is herbaceous to coriaceous, leathery, when fresh and papery when dried. Its shape ranges from ovate to obovate. The leaf can range from (I) densely pubescent on both sides with stellate hairs as in P. namaquanum to (II) glabrous on both sides in P. rutenbergainum to (III) pubescent to glabrous above and densely pubescent to glabrous beneath in other species. The apex is acuminate, pointed, to rounded or infrequently mucronate, ending abruptly in a small triangular tip on top, as in P. bispinosum, P. lamerei, and P. leali. Secondary veins in dried leaves are apparent in all species except P. bispinosum. These veins are paired, straight at the base and upcurved upwards.
Inflorescence
Pachypodium inflorescence are (I) terminal, the end of an axis, (II) sessile, lacking a stem, OR (III) pedunculate, the main axis of the inflorescence. With exception to P. geayi, the inflorescence is congested with few to many flowers. With the species P. bispinosum, P. lealii, and P. succulentum, the inflorescence is terminal on minute lateral branchlets. The inflorescence is thus often seen as axillary. The bracts are usually sepal-like, where they are pubescent on the outside and mostly glabrous inside, with exception to P. bispinosum, P. rutenbergainum, and P. saundersii. The latter three are glabrous on both sides. The peduncle, the main axis of the inflorescence, is 0-20 mm long in P. meridionale, P. rutenbergianum, P. sofience, and all continental African species. P. horombense sports the longest peduncles, often up to 56 mm. The flowers are sessile--lacking a stem. The longest pedicels are also found on P. horombense.
Flower
Calyx
A calyx is the outer most series of leaves in a flower, which are commonly green. That is to say, it is the collective term for all sepels of a flower; or the outer whorl of the perianth, where perianth is the protective envelop of the flower consisting of all uniform segments; such as tepals, or consisting of the calyx and corolla.
In Pachypodium, the calyx always has five subequal ovate to oblong sepals united at the base of the flower and is often persistent in the fruit.
Corolla
A corolla is a collective term used for all the petals of a flower; or the inner whorl of a perianth.
In Pachypodium, the corolla is tubular and variously colored; where the lobes are (I) red to crisom in P. baronii and P. windsorii; (II) pure white in P. meridionale and P. rutenbergainum; (III) yellow in many species from Madagascar; AND (IV) variously colored in other species. The mature corolla bud has a head that is usually oviod with an obtuse apex in all species except P. meridionale and P. rutenbergianum, which have narrowly oviod heads and an acuminate apex. The tube of the corolla is divided into two parts: (I) The basil part is usually cylindrical and often shorter than the upper part; with exception in P. densiflorum, P. geayi, P. inopinatum, and P. windsorii; AND (II) the upper part may be (a) urceolate--urn-shaped or hollow and with a contraction near the "mouth--in P. ambongense, P. decaryi, P. lamerei, P. lealii, P. rutenbergainum, and P. saundersii; (b) cylindrical in P. baronii, P. brevicaule, P. sofience, P. succulentum, and P. windsorii; AND (c) occonical in all other species. A pubescent belt is below the insertion of the stamens, which may continue upwards and may become more dense at the mouth in P. baronii and P. windsorii; or this pubescent belt may extend sometimes all over the lobes as in P. namaquanum. The corolla measures 9 mm long in P. succulentum and 60 mm long in P. sofiense. The corolla lobs overlap to the right in bud and are slightly twisted only in P. meridionale and P. rutenbergainum. In P. meridionale, the lobes are always longer than the tube; just as they are always shorter in P. bicolor, P. bispinosum, P. gracilius, P. horombense, P. namaquanum, P. saundersii, and P. sofiense. In other species, they can shorter or longer than the corolla tube. The corolla lobes are obliquely ovate or obliquely obovate, recurved in P. geayi, and undulate in P. densiflorum, P. lealli, P. meridionale, and P. rutenbergainum. The apex is acuminate to rounded.
Stamens and Pistil
The "male" organ within a flower, usually consisting of filament--the usually thin to thread-like short or elongated stalk of the stamen which carries the anther at the upper end--AND anther--the part on the stamen, usually on top, which bear the pollen, commonly consisting of two or four thecae which contain the pollen, and a sterile region in between the connective.
The ovary of the Pachypodium flower is subglobose and composed of two carpels--the "female" organ of an angiospermous flower that consists of a modified leaf that contains the ovules and normally has a style with a stigma at top. (A style is the commonly cylindrical or stalk-like portion that connects the stigma with the ovary, carpel; whereas the stigma is the top-most receptive region of the style, often divided into stigma-lobes, commonly papillate or wet by a sticky exudate to help capture and norish pollen grains.) These two carpels of the subglobose ovary is either pubescent or glabrous. Importantly each carples contains numerous ovules. All species of Pachypodium have stamens except P. desiflorum and P. geayi where they are exserted; or, thrust outward or protruding, as stamens projecting beyond petals.
Fruit
The fruit of Pachypodium are composed of two separate mericaps, the part of an ovary, or carpel, with one or more enclosed seeds; often the distribution unit of segmented fruits. Pale to dark brown, the mericarps of Pachypodium are marked with longitudinal lines or lenticellate outside; whereas inside, when dried, it is whitish to pale brown and either (I) glabrous for P. decaryi, P. geayi, P. meridionale, P. lealli, and P. saundersii; OR (II) densely pubescent in P. namaquanum; OR (III) pubescent to puberulous in the other species. The mericaps are usually fusiform--spindle-shaped or elongated and terete and gradually tapering at each end--with exception to P. namaquanum, where they are obovoid to ellipsoid.
Seed
The seed grains are pale to medium brown, have smooth to rough testa, and bear a single straw-colowered or whitish coma on their apex.
Habitats of Pachypodium of Madagascar and Southern Continental Africa
Study, Materials, and Methodology
A Larger Context for the Habitats of Pachypodiums
References
Taxonomy
GardenWeb (http://www..gardenweb.com)
Glossary of Botanical Terms with Special Reference to Succulent Plants. (Including German Equivalents) complied by Urs Eggli.(British Cactus and Succulent Society,
1993)
Pachypodium
Trees of Southern Africa by A. van Wyk and P. van Wyk
Pachypodium (Apocynaceae): Taxonomy, Habitats and Cultivation by S.H.J.V Rapanarivo; J.J Lavranos, A.J.M. Leeuwenberg and W. Röösli [Rapanarivo et al.].
Lavranos, John J. "Pachypodium makayense: A New Species from Madagascar." Cactus ands Succulent Journal(USA) 76 (2), 85-88.
External link
GardenWeb: Easy, General Taxonomy