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Coleocephalocereus purpureus has a cephalium; Micrantho - cereus streckeri has a pseudocephalium (, , Cactaceae) Root Gorelick Department of Biology, School of Mathematics & Statistics, and Institute of Interdisciplinary Studies Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6 Canada. (email: [email protected]). Photographs by the author

Summary : The putatively closely related Introduction genera of Coleocephalocereus , Micranthocereus , Cactaceae (cacti) in the tribe Cactoideae have Cereus , Monvillea , and Stetsonia have a wide a wide range of reproductive anatomies ranging range in specialization of reproductive portions of from cephalia to pseudocephalia to forms where the shoot, from cephalium to pseudocephalium to reproductive and vegetative structures are indis - no specialization. After briefly summarizing the tinguishable (Buxbaum, 1964, 1975; Mauseth, shifting uses of the terms ‘cephalium’ and ‘pseudo - 2006). cephalium’, I provide gross morphological evi - For instance, Link & Otto, Disco - dence that Coleocephalocereus purpureus has a cactus Pfeiffer, and Britton & Rose have true cephalium that is formed of a continuous true cephalia in which the flowering parts are not swath of bristles and hairs, with its underlying photosynthetic because every epidermal cell con - thick cortex of parenchyma replaced by a narrow tains a modified leaf that is a hair, bristle, or layer of cork. By contrast, Micranthocereus streck - spine, with no stomata amongst the epidermal eri has a pseudocephalium composed of nothing cells (Mauseth, 2006). Furthermore, there are more than larger hairier areoles in which the un - changes to the internal anatomy of cephalia, derlying epidermis is still photosynthetic and the where the underlying cortex is not a wide swath of underlying cortex is still a thick layer of highly succulent parenchyma, but instead a thin parenchyma without any noticeable cork. layer of cork. By contrast, pseudocephalia are composed of Zusammenfassung : Die vermuteterweise nahe relatively normal areoles that simply grew more miteinander verwandten Kakteengattungen hairs or bristles. The areoles themselves may also Coleocephalocereus , Micranthocereus , Cereus , be larger and closer to being confluent. The epi - Monvillea , und Stetsonia haben ein weites Spek - dermis of a pseudocephalium is still photosyn - trum an Spezialisierungen der reproduktiven thetic (chlorenchyma) with stomata, and the Sprossabschnitte, variierend von Cephalien zu underlying cortex is unchanged, with a thick layer Pseudocephalien, und ohne Spezialisierung. Nach of succulent parenchyma (Mauseth, 2006). As einer kurzen Zusammenfassung der im Laufe der with true cephalia, pseudocephalia usually grow Zeit unterschiedlichen Verwendungen der Be - directly from the shoot apical meristem, as in Pi - griffe `Cephalium' und `Pseudocephalium' stelle losocereus Byles & G.D. Rowley and Cephalocleis - ich allgemeine morphologische Evendenzen vor, tocactus F. Ritter (cf. Buxbaum, 1964). Many cacti dass Coleocephalocereus purpureus ein echtes with pseudocephalia are also like those with Cephalium hat, das aus einem kontinuierlichen cephalia in that flowers are only produced from Streifen aus Borsten und Haaren besteht, dessen specialized areoles, i.e. those with long copious darunterliegender dicker parenchymatischer Cor - hairs and bristles, although a few such as tex durch eine dünne Korkschicht ersetzt wird. Im Arrojadoa hofackeriana (P.J. & Esteves) P.J. Gegensatz dazu hat Micranthocereus streckeri ein Braun & Esteves [synonyms: Micranthocereus ho - Pseudocephalium, das lediglich aus grösseren und fackeriana (P.J. Braun & Esteves) Machado and stärker behaarten Areolen besteht, bei dem die Arrojadoa multiflora F. Ritter subsp. hofackeri - darunterliegende Epidermis weiterhin photosyn - ana P.J. Braun & Esteves] can produce flowers thetisch bleibt, und bei dem der darunterliegende from both the pseudocephalium and more juve - Cortex weiterhin aus einer dicken Parenchym - nile-looking (non-wooly) areoles (Braun & Esteves schicht besteht, ohne auffällige Korkbildung. Periera, 2007).

142 Bradleya 31/2013 Figure 1. gounellei subsp. zehntneri , Figure 2. Espostoa melanostele , radial section of with pseudocephalia arising from shoot apical young cephalium, with flower bud. meristems.

Figure 3. Espostoa melanostele , cross section (of Figure 4. Coleocephalocereus purpureus , in habi - excised section from Figure 2) with cephalium on tat. left.

Figure 5. Coleocephalocereus purpureus , shoot Figure 6. Coleocephalocereus purpureus , cross that was sectioned in Figures 6-8. section.

Bradleya 31/2013 143 My modest goal was to determine whether ium (e.g. Zavala-Hurtado et al., 1998, Valverde et Coleocephalocereus purpureus (Buining & al ., 2007). Similarly, Gürke (1908) used the term Brederoo) F. Ritter and Micranthocereus streckeri ‘cephalium’ for all specialized wooly floriferous Van Heek & Van Creik. have a cephalium or in - portions of cactus shoots, when speaking of stead a pseudocephalium. Both species are in the Facheiroa ulei (Gürke) Werderm. [as Cephalo - tribe Cereeae (Hernández-Hernández et al ., 2011), cereus ulei Gürke] and Micranthocereus pur - which contains with cephalia ( Melocactus , pureus (Gürke) F. Ritter [as Discocactus , Arrojadoa Britton & Rose), plants purpureus Gürke]. with pseudocephalia (several Pilosocereus Britton & Rose (1919-1923) confined use of the species), plants with neither a cephalium nor term ‘cephalium’ to Melocactus and Discocactus , pseudocephalium ( Cereus Miller; with the possi - calling all other specialized reproductive struc - ble exception of the enigmatic C. mortensenii tures ‘pseudocephalia’. A “cephalium [is] com - (Croizat) D.R. Hunt & N.P. Taylor), and a few posed of a central woody core surrounded by a plants that are ambiguous (e.g. Stetsonia coryne dense mass of long wool, bristles or both” (Britton (Salm-Dyck) Britton & Rose, which is like & Rose, 1922: 216). “Flowering areoles develop an Carnegiea gigantea Britton & Rose and Brown - abundance of wool which confluently forms a ingia candelaris (Meyen) Britton & Rose in only dense mass called a pseudocephalium either at flowering from relatively spineless areoles). the top or on one side near the top” (Britton & Surprisingly, there has been almost no pub - Rose, 1920: 25). Britton & Rose (1920) referred to lished work on the morphology of cephalia and all known species of Coleocephalocereus Backe - pseudocephalia. These structures have been sec - berg and Micranthocereus Backeberg as Cephalo - tioned and the results published on only a few cereus , which they claimed had pseudocephalia. cacti, such as Melocactus spp., Espostoa spp., Many subsequent authors followed Britton & Pfeiffer, C. columna-trajani Rose’s tradition of reserving the term ‘cephalium’ (Karw.) K. Schum., and Pachycereus militaris exclusively for Melocactus and Discocactus , e.g. (Audot) D.R. Hunt [synonym: Backebergia mili - Gibson & Nobel (1986). Anderson (2001: 697) even taris (Audot) Sánchez-Mej.] (Mauseth, 1999, 2006; more explicitly concurred with Britton & Rose by Mauseth et al ., 2005; Vázquez-Sánchez et al ., defining a pseudocephalium as “a lateral cephal - 2005, 2007), but apparently not on other taxa, ium”. such as the two species investigated herein. Backeberg (1934-1938) applied the term ‘cephalium’ to the following taxa (I have listed A short history of the terms cephalium and modern names, not Backeberg’s): Melocactus , Dis - pseudocephalium cocactus , Arrojadoa , Stephanocereus leucostele , The above distinction between cephalia and Facheiroa Britton & Rose, Espostoa , pseudocephalia is modern, with older literature Buxbaum, Coleocephalocereus , Cephalocereus , and even some current literature giving different and Neobuxbaumia macrocephala (F.A.C. Weber definitions of these two terms. I therefore give a ex K. Schum.) E.Y. Dawson. Backeberg only used brief history of the use of these terms. the term ‘pseudocephalium’ for Micranthocereus Hooker used the term ‘cephalium’ in several of and Pilosocereus Byles & G.D. Rowley. Note, how - his Latin diagnoses in Curtis’s Botanical Maga - ever, that he claimed that Cephalocereus pur - zine , but never defined the term and seemed to pureus Gürke and Cephalocereus macrocephalus use the term somewhat indiscriminately, for ex - F.A.C. Weber ex K. Schum. have cephalia, even ample, from a panoply of plants that we now usu - though I would label these plants Micrantho - ally call Melocactus intortus (Mill.) Urb. (1831, cereus purpureus (Gürke) F. Ritter and Vol. 58, Tab 3090), Parodia ottonis (Lehm.) N.P. Neobuxbaumia macrocephala , respectively, and Taylor (1831, Vol. 58, Tab 3107), Echinopsis say that they probably have pseudocephalia, as I eyriesii Turpin (1835, Vol. 62, Tab 3411), Gymno - believe do all Micranthocereus and Cephalocereus calycium gibbosum (Haw.) Pfeiffer ex. Mittler species that have specialized wooly flowering are - (1837, Vol. 64, Tab 3561) and Echinocereus oles. Backeberg (1934-1938) also noted whether rigidissimus Rose (1845, Vol. 71, Tab 4190). some lateral cephalia were channeled or sunken The earliest definition I could find of a ‘cephal - in a cleft, as in Coleocephalocereus fluminensis ium’ is “the floriferous region of the is dif - (Miquel) Backeberg, Espostoa lanata (Kunth) ferentiated from the rest” in Berger’s (1907: 61) Britton & Rose, and E. melanostele (Vaupel) Borg. description of the Cephalocereus Pfeiffer. Buxbaum (1964) said that cephalia and Nowadays, some would call the reproductive pseudocephalia are densely hairy regions of a structures of Cephalocereus a cephalium (e.g. shoot – hairier than vegetative parts of the shoot Vázquez-Sánchez et al ., 2005, 2007), while others – from which flowers originate. If these hairy re - – including me – would call this a pseudocephal - gions originated from the shoot apical meristem,

144 Bradleya 31/2013 Figure 7. Coleocephalocereus purpureus , cross Figure 8. Coleocephalocereus purpureus , radial section. section, showing apical meristem, flower buds (one or two), and a scintilla of chlorenchyma un - derneath cephalium (near curve).

Figure 9. Coleocephalocereus pur - Figure 10. Coleocephalocereus Figure 11. Coleocephalo - pureus with a 25 cm cephalium, shoot purpureus , radial section, show - cereus purpureus , radial sec - that was sectioned in Figures 10-11. ing replacement of thick tion, facing section of Figure parenchymous cortex with a thin - 9. ner cork layer as soon as cephal - ium starts.

Bradleya 31/2013 145 Buxbaum called the flowering region a cephalium. cephalium of Espostoa melanostele . The bottom If these hairy regions developed later as subse - quarter of the image grew before the cephalium quent growth on existing areoles, Buxbaum called formed and is radially symmetrical, with equally these flowering regions a pseudocephalium. thick cortex on both sides of the vascular cylinder Buxbaum (1975) realized that there is a contin - and lots of chlorenchyma on both sides of the uum between these two developmental extremes, shoot. No photosynthesis occurs underneath (cen - but never seems to have proposed an alternative tripedal to) the cephalium. A cross (horizontal) way to define points along this ontogenetic con - section of the same shoot (Figure 3) also shows ra - tinuum. dial asymmetry and lack of green photosynthetic There is also the problem that a cactus shoot tissue underneath the cephalium. Figure 11 in can do both. That is, an individual shoot can grow Buxbaum (1964) illustrates the confluent areoles wooly areoles directly from the shoot apical meris - in the cephalium, diminished cortex underneath tem and later grow more wooly modified spines as the cephalium, and diminished pith underneath the areoles slowly grows larger over the years the cephalium, albeit in Espostoa lanata (labelled (Gorelick, in review, a). By Buxbaum’s (1964) def - as E. sericata J. West). inition of a cephalium being wooly areoles pro - The cephalium in E. melanostele (and all other duced by the shoot apical meristem, species of Espostoa ; see Buxbaum, 1964; Mauseth, Micranthocereus and several taxa of Pilosocereus , 1999, 2006) grows from the shoot apical meristem such as P. gounellei (F.A.C. Weber ex. K. Schum.) and, very soon after initiation of cephalium Byles & G.D. Rowley subsp. zehntneri (Britton & growth, the shoot narrows on the cephalium-bear - Rose) Byles & G.D. Rowley [synonym: P. braunii ing side, with the shoot developing a thin but Esteves] (Figure 1), have cephalia, even though dense layer of cork underneath the cephalium in these are some of the few taxa that Backeberg lieu of a wide layer of parenchyma. Simultaneous (1934-1938) claimed had pseudocephalia. with formation of the cork layer, the highly suc - Buxbaum (1964) understood that lateral culent parenchyma layer of cork underneath the cephalia, at least of Espostoa , not only originated nascent cephalium diminishes. The only green tis - from the shoot apical meristem, but that the sue of the cephalium is the small side branch, cephalium was also sunken within the surround - which is a flower bud. Above that flower bud, the ing photosynthetic parts of the shoot and that the cork has almost entirely replaced the parenchy - vascular cylinder was flattened on the side of the mous cortex. Other than spines, the cork underly - shoot underlying the cephalium. He also under - ing the cephalium is the only difficult part to slice stood that the areoles were confluent in the when sectioning the plant. At the very top of the cephalium, with less prominent ribs and tubercles cork layer is the shoot apical meristem, which is near the transition between vegetative and repro - displaced from a vertically apical position, tilted ductive tissues. This presages Mauseth’s (2006) towards the cephalium-bearing side of the shoot. definition of a cephalium, which I have largely borrowed here. But curiously, Buxbaum never re - Coleocephalocereus purpureus and Micran - lied on these characteristics for differentiating thocereus streckeri cephalia from pseudocephalia, possibly because he Coleocephalocereus purpureus and Micrantho - had not sectioned many taxa. cereus streckeri may seem like odd choices for It is beyond the scope of this paper to justify study, especially since both are highly restricted which definitions of cephalia and pseudocephalia endemics of eastern Brazil and suspected of being are best. This is a difficult task insofar as defini - of recent hybrid origin (but of what parents?). tions are neither testable nor falsifiable. “Quality Coleocephalocereus purpureus (Buining & of a definition is gauged by its utility and consis - Brederoo) F. Ritter is sometimes confused with tency of meaning and connotation across many Micranthocereus purpureus (Gürke) F. Ritter (e.g. contexts” (Gorelick, 2012: 872). This is probably http://www.arkive.org/cactus/coleocephalocereus- why Buxbaum (1964) asked how did cephalia orig - purpureus/image-G72084.html; accessed 16 June inate and is there phylogenetic signal in pres - 2013; I have requested that this error be reme - ence/absence of cephalia and pseudocephalia. But died), which is somewhat expected given that answers to these questions will have to await an - some species have been transferred between these other day, Here, I simply want to describe gross two genera, e.g. M. albicephalus (Buining & morphological details of cephalia and pseudo - Brederoo) F. Ritter is synonymous with C. albi - cephalia in a few taxa. cephalus (Buining & Brederoo) F.H. Brandt. Cul - tivated specimens of both C. purpureus and M. Espostoa melanostele : a classic lateral streckeri were available for dissection and they cephalium eventually flowered, allowing unambiguous iden - Figure 2 shows a radial (vertical) section of a tification. Curiously, M. streckeri is like several

146 Bradleya 31/2013 Figure 13. Micranthocereus streckeri , double- sided cephalium with flowers and fruits.

Figure 12. Micranthocereus streckeri , in habitat.

Figure 14. Micranthocereus streckeri , both Figure 15. Micranthocereus streckeri , shoot that cephalia arising from one shoot apical meristem. was sectioned in Figures 16-17.

Figure 16. Micranthocereus streckeri , cross sec - Figure 17. Micranthocereus streckeri , cross sec - tion. tion.

Bradleya 31/2013 147 species of Espostoa in that a pair of lateral cal true cephalium. cephalia/pseudocephalia sometimes grows on dia - Figures 10-11 are of the pair of facing radially metrically opposite sides of a single shoot (Fig - sections of a 25 cm long cephalium of Coleo - ures 10-11), a phenomenon that is rare. Figures 4 cephalocereus purpureus , where the intact plant and 9 are habitat photos of C. purpureus at its is shown in Figure 9. At the shoot apical meris - type locality in Minas Gerais and of M. streckeri at tem – which is tilted far towards the cephalium- its type locality in Bahia. Figures 5 and 12 are bearing side and is at the top of the cephalium – photos of the cultivated plants of these two the cephalium occupies about half the circumfer - species, in flower, prior to sectioning. Figures 6-8 ence of the shoot. The cork immediately underly - and 16-17 are sections of Figures 5 and 15, re - ing the cephalium was the only portion that was spectively. difficult to cut. The cork layer varied in thickness In sectioning these plants, it was immediately as the cephalium grew, but the number of ribs obvious that Coleocephalocereus purpureus pos - that the cephalium covered also varied. Unlike sessed a true cephalium, while Micranthocereus with Espostoa melanostele , as soon as the cephal - streckeri possessed a pseudocephalium because ium appeared in C. purpureus , the succulent only the former had a cork layer that made cut - parenchyma in the cortex underlying the cephal - ting difficult, but only just underneath the surface ium immediately disappeared and was replaced of the cephalium. The rest of C. purpureus (except by the cork layer. Unlike in the smaller plant of for the spines) cut like butter, as is typical for C. purpureus in Figure 8, there is absolutely no young to middle-aged non-cephalium-bearing cac - evidence of chlorenchyma underlying this much tus shoots (old columnar cacti sometimes develop larger cephalium (close-ups not shown). a corky base). There is a very similar localized re - The cross section in Figures 16-17 is through sistance to cutting the cork layer underlying the the widest portion of the pseudocephalium of the cephalia of Melocactus and Discocactus (Gorelick, Micranthocereus streckeri shoot, near the pair of in review, b). By contrast, all portions of the shoot mature red fruits in Figure 15. Even before sec - of Micranthocereus streckeri , including the tioning the shoot, it was somewhat obvious that pseudocephalium, cut like butter. the pseudocephalium is formed from simply a part The cephalium of Coleocephalocereus pur - of the shoot with larger and hairier areoles, even pureus is not on the ribs, but rather occupies a though these grew right from the shoot apical continuous area that goes on top of and between meristem. Note how the pseudocephalium did not ribs (Figures 5-7). For the most part – although disrupt phyllotaxy. As the cephalium grew wider see below for a small exception – there is no obvi - and then narrower again in Figure 15, the ribs ous photosynthetic tissue underneath the cephal - continued on through in a straight line, with un - ium, while hairs and bristles in the cephalium derlying architecture of the ribs remaining un - seem to arise from every epidermal cell (Figures 6- changed. The cross section shows photosynthetic 8). The cork layer underneath the cephalium is ob - tissue in between areoles, as well as underneath vious in Figure 10, where the cork has a brown them (Figure 16). The cross section of the shoot is colour compared with the white of the succulent circular, i.e. radially symmetrical, with no obvious parenchyma underneath the surface of photosyn - cork formation underneath the flowering areoles thetic tissue. Because the cephalium of C. pur - (Figure 17). Micranthocereus streckeri has a typi - pureus in Figures 5-8 was young and small, the cal pseudocephalium, sensu Mauseth (2006). radial section of the upper half of the cephalium plus adjacent photosynthetic tissue (Figure 8) was Concluding remarks not as elegant as that of Espostoa melanostele . Based on five characters – (1) cork, (2) radial Nonetheless, a comparison of Figures 2 and 8 asymmetry, (3) chlorenchyma, (4) confluent are - shows very similar architecture. The dark green oles, and (5) phyllotaxy – Coleocephalocereus pur - from which the two short bristles at the top of Fig - pureus has cephalia, whereas Micranthocereus ure 8 are growing is the shoot apical meristem of streckeri has pseudocephalia. C. purpureus . This radial section sliced through Hernández-Hernández et al . (2011) show a vir - one fairly large flower bud, which looks like a tual polytomy in the tribe Cereeae with the five small side shoot. Not far above that flower bud is genera Coleocephalocereus Backeberg, Micran - probably the start of another flower bud, which thocereus , Cereus , Monvillea Britton & Rose, and also shows the red colour of the perianth parts. Stetsonia Britton & Rose. Specialization of repro - The only thing surprising in this radial section is ductive structures can clearly vary greatly across the very small amount of chlorenchyma that ap - a clade. It is even possible that within a single pears in the apparent curve in the cephalium. genus that there may be species with cephalia and This may be because the cephalium is young. Oth - pseudocephalia or with pseudocephalia and no erwise, Coleocephalocereus purpureus has a typi - specialization into morphologically distinct flow -

148 Bradleya 31/2013 ering areoles, such as possibly with Pilosocereus , GORELICK , R. (in review, a) Axillary branching of Stephanocereus A. Berger, or Micranthocereus . lateral cephalia in Cactaceae is not con - However, it appears that all species of Coleo - strained by tilting of shoot apices. Haseltonia . cephalocereus have a true cephalium because the GORELICK , R. (in review, b) Circular meristem at hairs and bristles appear to be independent of the base of terminal cephalia in Discocactus (Cac - phyllotaxy, i.e. independent of the ribs, whereas taceae). Madroño . no species of Micranthocereus have a true cephal - ium because you can distinguish individual are - GÜRKE , M. (1908) Neue Kakteen-Arten aus oles in the pseudocephalium and these rows of Brasilien. Monatsschrift für Kakteenkunde 18 : areoles line up nicely with those of the older green 84-89. non-reproductive portions of the shoot (Taylor & HERNÁNDEZ -H ERNÁNDEZ , T., H ERNÁNDEZ , H.M., Zappi, 2004). Pseudocephalia and cephalia may be DE-N OVA , J.A., P UENTE , R., E GUIARTE , L.E., & homologous, with the pseudocephalia merely hav - MAGALLÓN , S. (2011) Phylogenetic relation - ing chlorenchyma and stomata, while lacking the ships and evolution of growth form in Cac - thin cork layer in the cortex. But the only way to taceae (, Eudicotyledoneae). test such a hypothesis is to start by collecting nat - American Journal of Botany 98 : 44-61. ural history observations of the gross morphology MAUSETH , J.D. (1999) Comparative anatomy of Es - of these flowering regions. postoa , Pseudoespostoa , Thrixanthocereus and Vatricania (Cactaceae). Bradleya 17 : 27-37. Acknowledgments Thanks to the Natural Sciences and Engi - MAUSETH , J.D., T ERRAZAS , T., V ÁZQUEZ -S ÁNCHEZ , neering Research Council of Canada (NSERC) for M., & A RIAS , S. (2005). Field observations on funding. Thanks to an anonymous reviewer for Backebergia and other cacti from Balsas helpful suggestions and to Graham Charles for Basin, Mexico. Cactus and Succulent Journal generously providing reprints of Buxbaum’s pa - (US) 77 : 132–143. pers. MAUSETH , J.D. (2006) Structure-function relation - ships in highly modified shoots of Cactaceae. References Annals of Botany 98 : 901-926. ANDERSON , E.F. (2001) The Cactus Family . Tim - TAYLOR , N.P. & Z APPI , D.C. (2004) Cacti of East - ber Press, Portland. ern Brazil . Kew, Surrey, England. BACKEBERG , C. (1934-1938) Blätter für Kakteen - forschung . VALVERDE , P.L., V ITE , F, P EREZ -H ERNANDEZ , M.A., AVALA URTADO BERGER , A. (1907) A systematic revision of the & Z -H , J.A. (2007) Stem tilting, genus Cereus Mill. Missouri Botanical Garden, pseudocephalium orientation, and stem al - Annual Report 1905 : 57-86. lometry in Cephalocereus columna-trajani BRAUN , P.J. & E STEVES PERIERA E. (2007) Beauti - along a short latitudinal gradient. Plant Ecol - ful and bizarre Arrojadoa : the of ogy 188 : 17-27. subgenus Albertbuiningia . Cactus and Succu - VÁZQUEZ -S ÁNCHEZ , M., T ERRAZAS , T., & A RIAS , S. lent Journal (US) 79 : 254-263. (2005) Morfología y anatomía del cefalio de BRITTON , N.L. & R OSE , J.N. (1919-1923) The Cac - Cephalocereus senilis (Cactaceae). Anales del taceae . Carnegie Institution, Washington DC. Jardín Botánico de Madrid 62 : 153-161. (Volume 1 – 1919; Volume 2 – 1920; Volume 3 VÁZQUEZ -S ÁNCHEZ , M., T ERRAZAS , T., & A RIAS , S. – 1922; Volume 4 – 1923). (2007) Morphology and anatomy of the BUXBAUM , F. (1964) Was ist ein cephalium? Kak - Cephalocereus columna-trajani cephalium: teen und andere Sukkulenten 15 : 28-31, 43-49. Why tilting? Plant Systematics and Evolution BUXBAUM , F. (1975) Ergebnisse der Kakteen - 265 : 87-99. forschung von 1962 bis 1973. III. Von Prae - cereus zu Pseudopilocereus . Kakteen und ZAVALA -H URTADO , J.A., V ITE , F., & E ZCURRA , E. andere Sukkulenten 26 : 6-9 (1998) Stem tilting and pseudocephalium ori - GIBSON , A.C. & N OBEL , P.S. (1986). The Cactus entation in Cephalocereus columma-trajani Primer . Harvard University Press, Cam - (Cactaceae): a functional interpretation. Ecol - bridge. ogy 79 : 340-348. GORELICK , R. (2012) Mitosis circumscribes indi - viduals; sex creates new individuals. Biology & Philosophy 27 : 871-890.

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