CoronaCactus Gardens and Nursery

Probably the most popular of cephalia cacti are the Melocactus species. Often shown in photos with tall white/red/pink cylinders growing out of the top of the cactus.

However, there are many other types of cacti that also produce a cephalium. Many columnar species produce a lateral cephalium that starts at the top of the stem and grows down. Some plants have long cephaliums, while others have short ones.

No matter the specie or shape, all cephalia cacti need to reach maturity before they can produce the cephalium. This means that they cannot reproduce themselves (i.e.; grow flowers or fruit) until the plant has reached a certain age and the cephalium has grown out.

In some species, flowers and fruit can follow very quickly once the cephalium has been produced. While other species require more time.

Fig. 1

Myrtillocactus geometrizans

Photo: Gerard Ardisson's Cactus & Succulents Photo Gallery

How and why the cephalium evolved are indeed quite interesting questions. This structure evolved several times in the family, in many independent groups both in North America and in South America. Thus, there must be a very good reason for so many different plants have evolved similar structures.

With a few exceptions, each areole of all cacti produce a single flower, and that is it - after this flower is produced, the areole becomes inactive. Exceptions to this rule are Myrtillocactus in North America, which can produce several flowers per areole: (fig. 1)

Fig. 2

Neoraimondia gigantea

Photo: Mauseth's Lab

and Neoraimondia in South America, whose areoles not only produce several flowers per areole but they also flower year after year, the areole growing each year and becoming longer, like a miniature cephalium: (fig. 2)

Regarding the Neoraimondia and it�s elongated areoles:

Is this an evolutionary stepping stone towards cephalia?

Actually the areoles of Neoraimondia, although cephalium-like, are quite distinct from a normal cephalia and unlike anything else. They are not stepping stones towards cephalia. The areoles of the cephalium in cephalic cacti are like any other areole in that it becomes inactive after it has flowered. Areoles of the cephalium differ from areoles of the vegetative body of the same plant because they are capable of flowering, and because these areoles produce lots of wool and bristles. But once it has flowered, the areole of the cephalium becomes inactive like any other areole.

However, the areoles of Neoraimondia are different in that they are capable of growing year after year and producing flowers many times. These areoles are more like miniature branches than normal areoles, and they are similar to the cephalium of cephalic cacti, but yet distinct and quite unique.

But these exceptions aside, what usually happens in cacti is that once an areole has produced a flower and fruit, it becomes inactive. So, in order to produce more flowers, the cactus has to grow more areoles. And to grow more areoles the cactus has to grow it�s stem. However, the growth of new stems can be a very costly effort - for each new few centimeters of stem, the plant has to produce lots of inner tissue, epidermis, etc. which demands lots of energy and nutrients. From a cost/benefit perspective, it can be very costly to produce flowers and seeds for reproduction if each time the cactus has to grow new stems and thus spend a lot of energy in the process.

Many cacti devised clever ways of minimizing the amount of energy spent for reproduction by producing more areoles in a smaller area, thus producing more flowers without having to grow significant amounts of new stem. Take for example Astrophytum myriostigma. Young plants of this species have areoles well-spaced along the ribs: (fig. 3)

but as the plants grow older the areoles are produced at closer intervals, and big mature specimens have a continuous line of areoles along the ribs: (fig. 4)

Thus, a mature Astrophytum myriostigma reaches a good balance where it can produce lots of new flowers each year without having to spend too much energy in growing its stem.

Fig. 3

Astrophytum myriostigma

Photo: http://www.succulente.info/

Fig. 4

Astrophytum myriostigma

Photo: Wikipedia Astrophytum page

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Fig. 6

Lophocereus schottii

(=Pachycereus schottii)

Another example is the Senita Cactus, Lophocereus schottii, (=Pachycereus schottii) which is a columnar cactus species from northweastern Mexico and southern Arizona, US: (fig. 5)

Juvenile stems have well-spaced areoles: (fig. 6)

Which in maturity will develop very closely spaced areoles,

with long spines: (fig. 7)

�Fig. 5�� Fig. 7��

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Lophocereus schottii

(=Pachycereus schottii)

Photos: http://cactiguide.com/

Fig. 8

Melocactus zehntneri

Photo: Marlon Machado

Fig. 9

Discocactus placentiformis

Photo: Marlon Machado

Fig. 10

Backebergia militaris

Photo: Mauseth's Lab

Cacti that develop a cephalium just took it a step further on this concept of saving energy while maximizing reproduction potential. In cacti with cephalia, the reproductive parts of the stem are composed of very closely spaced areoles, so that many flowers can be produced with a minimal amount of energy spent with the growth of its stem. There are various types of cephalium:

apical cephalia like those produced by Melocactus: (fig. 8) Discocactus: (fig. 9) and Backebergia: (fig. 10)

I always understood all apical cephalia were in fact modified flowering branches. Is this wrong?

Yes, the apical cephalium is a modified portion of the stem whose function is reproduction - the production of flowers, however it is not a separate branch, it is a continuation of the vegetative stem. The meristematic cells at the apex of the juvenile stem undergo a phase change and switch to the production of adult characteristics.

lateral cephalia like those produced by, among others, Cephalocereus: (fig. 11) Espostoa: (fig. 12) Coleocephalocereus: (figs. 13, 14, 15 & 16)

Fig. 11

Cephalocereus senilis

Photo: [www.astrobase.de]

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Fig. 12

Espostoa guentheri

Photo: Philippe Corman http://www.cactuspro.com/

Fig. 13

Coleocephalocereus aureus

Photo: Marlon Machado

Fig. 14

Coleocephalocereus purpureus

Photo: Marlon Machado

Fig. 15

Coleocephalocereus buxbaumianus

Photo: Marlon Machado

Fig. 16

Gerard Delanoy with Coleocephalocereus goebelianus

Photo: Marlon Machado

Fig. 17

Arrojadoa dinae

Photo: Marlon Machado

and apical cephalia with recurrence of vegetative growth (ring cephalia) like those of Arrojadoa: (figs. 17, 18 & 19) and Stephanocereus: (figs. 20 & 21)

Fig. 18

Arrojadoa rhodantha

Photo: Marlon Machado

Fig. 19

Arrojadoa marylanae

Photo: Marlon Machado

Fig. 20

Gerard Delanoy with

Stephanocereus leucostele

Photo: Marlon Machado

Fig. 21

Stephanocereus leucostele

Photo: Marlon Machado

Besides the energy-saving benefit, the cephalium also has another great advantage, which is to afford protection to the flowers and fruits while they are still developing. The areoles of the cephalium usually produce copious amounts of bristles and wool which protect the young flower buds until they are ready to open, and also the young fruits until they are ripe. The flower buds and young fruits are hidden within the cephalium, enveloped by the bristles and wool, and not visible until they are mature enough to appear in the surface of the cephalium.

This is a very interesting subject indeed, and a good place to find more information about the cephalium is the website of Prof. Dr. James D. Mauseth. His text is very instructive, but beware that he uses a lot of technical terms. And, if you still want to learn more, there is an excellent review also published by Mauseth:

Mauseth, J.D. 2006. Structure?Function Relationships in Highly Modified Shoots of Cactaceae. Annals of Botany 98: 901?926.

I wonder why more South American cacti produce cephalia when compared to North American?

This is also an interesting question. Cephalium-bearing cacti occur in three tribes of Cactaceae:

Pachycereeae: Cephalocereus, Pachycereus (Backebergia)

Trichocereeae: Oreocereus (Morawetzia), Espostoa (including Pseudoespostoa, Vatricania, Thrixanthocereus, Binghamia), Cleistocactus (Cephalocleistocactus), Facheiroa, Espostoopsis, Discocactus

Cereeae: Melocactus, Micranthocereus (including Austrocephalocereus and Siccobaccatus), Coleocephalocereus (including Buiningia), Arrojadoa, Stephanocereus, Pilosocereus (a few species), Cereus (Cereus mortensenii)

The investigations that I and some colleagues are conducing here at the University of Zurich about the relationships among the genera of the Browningieae, Cereeae and Trichocereeae (the so-called BCT clade) using DNA sequence data have shown that Facheiroa, Espostoopsis, and Discocactus actually belong to the tribe Cereeae, not to the Trichocereeae. Thus, the distribution of the cephalium-bearing genera among the tribes is actually:

Pachycereeae: Cephalocereus, Pachycereus

Trichocereeae: Oreocereus, Espostoa, Cleistocactus

Cereeae: Melocactus, Micranthocereus, Coleocephalocereus, Arrojadoa, Stephanocereus, Pilosocereus, Cereus, Facheiroa, Espostoopsis, Discocactus

Thus, Pachycereeae has two genera with plants that develop a cephalium, Trichocereeae has three genera, and Cereeae has ten - five times more than the Pachycereeae, and three times more than the Trichocereeae!

Cereeae is not only rich in genera that develop cephalia, but it is also harbours a great diversity in cephalium forms - there are genera with apical, lateral, and ring cephalia. Why the Cereeae have so many genera with cephalium-bearing plants?

Unfortunatelly there is still no answer for this question. Further research is necessary to better undertand the evolution of the cephalium in the Cereeae. However, from my investigations I can tell that all members of the Cereeae are very closely related to each other, and all genera are very young - in spite of their differences in morphology, there are few genetic differences among the members of the tribe.

It is possible that the genes that code for the production of cephalium were already present in the ancestors of the whole group, and that as the members of the Cereeae diversified these genes evolved to code for different cephalium forms.

Thus, perhaps the answer to the question "why there are more cephalium-bearing genera in South America than in North America" may be that many of the cephalium-bearing cacti from South America have a common origin, and their ancestors probably already had a cephalium or a rudimentary form of it.

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Melocactus sp. cephalium cut away showing how the fruits are kept within the cephalium while they are unripe, thus protecting them.

Photo: Rosineide Fonseca

Melocactus paucispinus

Prepared to be dried up and mounted as a herbarium specimen.

Photo: Marlon Machado

A question about the lateral cephalia: Some seem to be on the sunny side and others on the shady side.

Of course they could be taken at different times of the day. Is there a preferred side for cephalia?

The cephalium usually develops in the sunniest side of the plant, which in South America is northwest, while in North America is southwest. In habitat, usually all plants in a population of a cephalium-bearing species have their cephalia turned to the same direction; see examples in the pictures below:

A few plants of Coleocephalocereus goebelianus, cephalia facing the same direction, photographed near Mato Verde, Minas Gerais.

Photo: Marlon Machado

A population of Micranthocereus dolichospermaticus, again all the plants have their cephalia facing the same direction, photographed near Porto Novo, Bahia.

Photo: Marlon Machado

The illustration of Stephanocereus luetzelburgii in the New Cactus Lexicon makes it look as though the

adult growth is just a narrowed form of the younger growth, is that so?

Does it actually constitute a cephalium in that case?

Stephanocereus luetzelburgii is a fascinating plant. Young plants have thick stems, and areoles with a few short, strong spines. However, when it reaches maturity the stem becomes thinner, the areoles are produced more closely spaced, and the areoles start to develop lots of wool and longer bristly spines. The areoles in the juvenile portion of the body are incapable of flowering, while the areoles produced by the mature stem are capable of flowering.

This marked phase change from juvenile to adult characteristics is very similar to what occurs in cacti that produces apical cephalia, like Melocactus and Discocactus, and the mature region of the stem of Stephanocereus luetzelburgii could be considered a cephalium-like structure. However, there are differences: in the cephalium of Melocactus or Discocactus, the areoles are much more closely spaced, so densely crowded that there is little space left between the areoles; also, plant of these genera lose the structure of ribs, and the cephalium is composed of spirals of indistinct tubercles upon which are the areoles. The epidermis of the cephalium does not have chlorophyll, and is quickly converted to bark.

Stephanocereus luetzelburgii differs in that it does not lose the structure of the ribs (the ribs may increase in number, but are still there) and although the areoles of the mature portion of the stem are more closely spaced, there is still space between the areoles (and between the ribs) and the epidermis is green, with chlorophyll.

There have been speculations as if the mature region of the stem in Stephanocereus luetzelburgii is homologous to the cephalium of Melocactus or Arrojadoa, that is, if they have the same evolutionary origin, or if these structures are merely analogous to each other (similar in function but having not the same evolutionary origin).

My studies on the relationships of the genera of the tribe Cereeae have shown that Stephanocereus luetzelburgii is the oldest lineage in the Arrojadoa clade (which is composed by Arrojadoa, Pierrebraunia bahiensis, Stephanocereus leucostele and Stephanocereus luetzelburgii), and this Arrojadoa clade is sister to the Melocactus clade (composed of Melocactus, Discocactus and Coleocephalocereus). Thus, the mature region of the stem in Stephanocereus luetzelburgii appears to be homologous to the cephalium of Melocactus and Discocactus, and could be regarded as a kind of proto-cephalium, a step in the direction of producing true apical cephalia.

True apical cephalia occurs in both Melocactus and Arrojadoa, the last differing from the former only because it can resume the production of vegetative growth - new stems - after it has produced a cephalium, hence the rings of cephalia in Arrojadoa. The mature region of the stem in Stephanocereus luetzelburgii could be a primitive version of the cephalium that later evolved in Melocactus, Discocactus, Arrojadoa and Stephanocereus leucostele. However, more detailed studies of the anatomy and morphogenesis (the differentiation and growth of tissues) in these species are necessary to better understand the similarities and differences among the several forms of cephalia in these cacti.

Below are some pictures of Stephanocereus luetzelburgii:

Young plant, just developing the mature portion of the stem.

Photo: Marlon Machado

Old plant in fruit

Photo: Marlon Machado

Mature plant, with a marked distinction between juvenile and adult portions of the stem.

Photo: Marlon Machado

Close-up of the apex of one specimen with an open flower and an young fruit.

Photo: Marlon Machado

Frontal view of the flower of the same specimen illustrated above.

Photo: Marlon Machado

Close-up of the apex of one specimen with a nearly ripe fruit. Photo: Marlon Machado

Perhaps you could shed some light on the plant below whilst on the subject of cephalium producing cacti. I photographed it whilst in Mexico in 2005 in the state of Puebla. Looking through the NCL it appears to be a Pilosocereus but which species I'm not sure.

The plant in your picture is most definitively a Pilosocereus, and the species whose description in the NCL more closely agrees with the appearance of the plant in your picture is Pilosocereus chrysacanthus - moreover, this species occurs in Puebla. (fig. 22)

However, the woolly parts of the stems are not a cephalium - the flowering areoles of many Pilosocereus species produce lots of wool and sometimes are all arranged in just one side of the stem, but there is no modification of the stem, and these flowering areas are not a cephalium. They are more appropriately called flowering zones. Some species can have very wooly flowering areoles, the most bizarre being those produced by Pilosocereus densiareolatus: (fig. 23)

Fig. 22

Pilosocereus chrysacanthus

Puebla, Mexico 2005

Photo: Vic (BCSS)

Fig. 23

Pilosocereus densiareolatus

Photographed near Porto Novo, Bahia.

Photo: Marlon Machado

Another species with an interesting flowering zone is

Pilosocereus fulvilanatus

With a continuous line of very wooly areoles along the ribs.

Photographed at Gr�o Mogol, Minas Gerais.

Photo: Marlon Machado

And the nice white fluff wool of the areoles of

Pilosocereus pachycladus

Photographed at Pedra Azul, Minas Gerais.

Photo: Marlon Machado

But there are a few species of Pilosocereus that develop a true cephalium, for example Pilosocereus diersianus and Pilosocereus gounellei - the development of a cephalium is variable in this last species, with some populations having no cephalium whatsoever, some populations having a very wooly flowering zone, and a few populations developing a true cephalium.

Pilosocereus gounellei

From a population that does not develop a cephalium.

Photographed at Morro do Chap�u, Bahia

Photo: Marlon Machado

Pilosocereus gounellei

From a population that does not develop a cephalium.

Photographed at Morro do Chap�u, Bahia.

Photo: Marlon Machado

Specimens of Pilosocereus gounellei from a population that does develop a cephalium - this form was described as a distinct species, Pilosocereus braunii. Photographed near Porto Novo, Bahia. (figs. 24, 25 & 26)

Fig. 24

Photo: Marlon Machado

Fig. 25

Photo: Marlon Machado

Fig. 26

Photo: Marlon Machado

You say that the Pilosocereus chrysacanthus (fig. 22) doesn't bear a cephalium yet there are some in that

genus that do. Now I would have thought that cephalium bearing is a genetic trait. i.e. that all plants with

cephalia belong to the same group (clade?) and that if one Pilosocereus develops a

Cephalium, then they all must do to belong in that group?

Yes, the cephalium is a genetic trait but it evolved many times in different groups of cacti, and for that reason it cannot be considered as a decisive characteristic for grouping species together, because in spite of having the same function, they may not have the same origin. For an easy example of what I mean, think of a bird, a bat, and a butterfly: they all have wings and fly, but they are not closely related and belong to quite distinct classes of animals: avian, mammal and insect.

So, not all plants with cephalia belong to the same group.

A clade is a group of organisms that are descendent from the same ancestor organism. It is just a term that biologists use to indicate common ancestry of the members of a group. All cacti form a clade because they all evolved from a single ancestor, but all succulents do not form a clade because succulents are a group of plants which have many different origins. The term clade can be used for any groups of organisms, as long as they have a common origin.

Now to the second part of your doubt, which is if one species of a group has one characteristic, all species should have that characteristic in order to belong in that group. That is not necessarily true. If we were to apply this rule then every species would need to be in its own genus, family, etc. because there are no two species alike. As a matter of fact, no two individuals are the same, unless they are clones of each other; thus, if the same principle were to be applied, each individual would be its own species, genus, family etc.

Of course we group species in genera or families based on shared characteristics. But the key here is that the characteristics have to be shared, that is, common to all species - provided of course that these species have a common origin (remember the example of the wings). Thus, what brings all cacti together among others are the characteristics of possessing areoles and having flower parts surrounded by stem tissue; what brings all Opuntioideae together are the development of glochids and arillate seeds (seeds enveloped by a tan to brownish woody or corky membrane); and so on.

In the case of Pilosocereus, what brings all the species of this genus together are characteristics of their fruits: all Pilosocereus develop naked depressed-globose fruits, opening by irregular slits at the apex and sides of the fruit, and the fact that the floral remnants are persistent, remaining attached to the fruits until they are ripe, and are deeply inserted in the fruit apex.

Back to the cephalium. Not all species of genera that have cephalium-bearing species necessarily develop a cephalium. For instance, in the large genus Pachycereus the only species that develop a cephalium is Pachycereus militaris; likewise the only species in the large genus Cereus that develop a cephalium is Cereus mortensenii. In Pilosocereus only two species are know to develop a cephalium: Pilosocereus diersianus and Pilosocereus gounellei - and in the last species the development of a cephalium is quite unstable, just a few populations do it, the majority don't - the cephalium is not yet a fixed characteristic in this species.

Other genera that have plants with and without cephalium are Facheiroa and Micranthocereus. In Facheiroa some species have well developed cephalia, for example Facheiroa ulei: (figs. 27 & 28)

Regarding the name Pilocereus, it was an older name used for the plants that now belong to the genus Pilosocereus, however the name Pilocereus was originally described by Lemaire for the plant that we know today as Cephalocereus senilis. Along the years many other columnar plants that had hairy areoles were described in the genus Pilocereus, but these new species were not closely related to the original Pilocereus which was Cephalocereus senilis. Karl Schumman tried to solve the problem and used the name Pilocereus exclusively for the species we recognize today as belonging to Pilosocereus, however this was unfortunate because it was against the rules of botanical nomenclature, and his version of Pilocereus became an illegitimate name. For this reason in 1957 Byles & Rowley described the new genus Pilosocereus to include the species not related to Cephalocereus senilis, and the choice of the name Pilosocereus was to make it as similar as possible to the older but invalid name Pilocereus.

In short, Pilocereus was used by two different authors to indicate two different genera, and for this reason the name became invalid: some species that used to be Pilocereus were retained in the genus Cephalocereus, while the remaining are now Pilosocereus.

Fig. 27

Facheiroa ulei

Photographed at Gentio do Ouro, Bahia.

Photo: Marlon Machado

Fig. 28

Facheiroa ulei

Close up of a mature branch with cephalium and fruit.

Photographed at Gentio do Ouro, Bahia.

Photo: Marlon Machado

While other species have no cephalium at all, for example Facheiroa squamosa: (figs. 29 & 30)

Fig. 29

Facheiroa squamosa

Photographed at Ju�, Bahia.

Photo: Marlon Machado

Fig. 30

Facheiroa squamosa

Close up of a mature branch with flower buds, no sign of cephalium.

Photographed at Ju�, Bahia.

Photo: Marlon Machado

And a few species are "undecided", some plants develop a cephalium while others do not, and some plants are even "in between" producing very dense flowering zones, or some branches having a cephalium while other branches in the same plant flowering without a cephalium, for example Facheiroa estevesii - the cephalium is not yet a fixed characteristic in this species: (figs. 31 & 32)

Fig. 31

Facheiroa estevesii

Photographed at Iuia, Bahia.

Photo: Marlon Machado

Fig. 32

Facheiroa estevesii

Close up of a mature branch with fruit, cephalium not fully developed.

Photographed at Iuia, Bahia.

Photo: Marlon Machado

The same situation occurs in the genus Micranthocereus, with some species developing a cephalium while others have only a flowering zone in the lateral of the stems. Even if you ignore the species of Micranthocereus subgen. Austrocephalocereus and Micranthocereus subgen. Siccobaccatus, where all species in both subgenera develop cephalium, and focus only the species of Micranthocereus in the strict sense (that is Micranthocereus subgen. Micranthocereus), where all species have the characteristic of producing masses of small, colorful flowers, you will still find that some species develop a cephalium, for example Micranthocereus streckeri: (figs. 33 & 34)

Fig. 33

Micranthocereus streckeri

Photo: Marlon Machado

Fig. 34

Micranthocereus streckeri

Photographed near Seabra, Bahia

Photo: Marlon Machado

While others possess only a flowering zone, like Micranthocereus auriazureus: (figs. 35 thru 42)

Fig. 35
Micranthocereus auriazureus

Photographed at Gr�o Mogol, Minas Gerais.

Photo: Marlon Machado

Fig. 36

Micranthocereus auriazureus

Close-up of a plant in flower, no sign of cephalium.

Photographed at Gr�o Mogol, Minas Gerais.

Photo: Marlon Machado

Fig. 37

Micranthocereus flaviflorus

Photographed at Morro do Chap�u, Bahia.

Photo: Marlon Machado

Fig. 38

Micranthocereus flaviflorus

Close-up of a plant in flower, no sign of cephalium, only a woolly flowering zone.

Photographed at Morro do Chap�u, Bahia.

Photo: Marlon Machado

Fig. 39

Micranthocereus polyanthus

(The type species)

Photographed at Brejinho das Ametistas, Bahia.

Photo: Marlon Machado

Fig. 40

Micranthocereus polyanthus

(The type species)

Close-up of a plant in flower, no sign of cephalium, only a woolly flowering zone.

Photographed at Brejinho das Ametistas, Bahia.

Photo: Marlon Machado

Fig. 41

Micranthocereus hofackerianus

(The newest discovered specie)

Photographed at Piat�, Bahia.

Photo: Marlon Machado

Fig. 42

Micranthocereus hofackerianus

(The newest discovered specie)

Close-up of a plant in flower, no sign of cephalium, only a woolly flowering zone.

Photographed at Piat�, Bahia.

Photo: Marlon Machado

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