Issue 30:
Cissus
(with photo)
by Emy de la
Fuente, Jr. Cereus Chatter, South Florida
C&S Aloe Polyphylla by Sue Haffner When Bad Things Happen To Good
Cacti by Sue Haffner Is It a Succulent? or Is It a Cactus?
by Lou Kilbert
Quizzical Plants: Monstrose and Crested Succulents
(with photos)
Cuttings by Dick Kohlschreiber
Photos from Minas Gerais, Brazil by Nels Christianson Sunset Succulent
Society (Photos &
captions) In Defense of Dactylopsis
Cissus by Emy de la
Fuente, Jr. Cereus Chatter, South Florida
C&S
Photo, click here about 15kB
When we think of the genus Cissus, we usually think of
its best known succulent species, Cissus quadrangularis and C.
tuberosa .
C. quadrangularis
is native to southern and
eastern Africa and from Arabia to India.
As its name indicates, it bears four-sided stems and three-lobed
leaves. It tolerates a wide range
of environments from full sun to shade.
From Cactus Corner
News
From Cactus Corner
News
Spinal Column, Michigan C&S
by L.
M. Moe The Cactus Patch,
Bakersfield, CA
The Epi-Gram Palos Verdes, CA July
2003
By Matthew R. Opel
San Francisco Succulent and Cactus Society Newsletter
C. tuberosa, a native of Mexico. It bears deciduous tendrils, which it
sheds in severe droughts. Its
greenish, woody like tuber has interesting markings.
However, there are about 200 species of these climbing
plants, which are natives of several tropical and subtropical countries. They are members of the Family
Vitaceae, which is best known for plants of the species Vitis
vinerifera, or the grape.
C. trifoliata
with a wide range of distribution from southern USA to Mexico to the
Caribbean has very tuberous roots
and 4 to 6 ridged warty stems .
C. discolor
from Indonesia bears leaves
which appear to be a bit more succulent, but not much. It bears ovate, velvety
green leaves mottled with silvery white and reddish-purple underneath Its flowers are deep
purple.
C. antarctica,
native of Australia is shrubby and climbs along with tendrils. It has shiny,
green leaves with brown veins and stems. It is not very succulent at
all.
Another very leafy species is C. rhombifolia with
its hairy brown branches and shiny green leaves that have fuzzy, white
undersides. It also climbs
with the aid of tendrils. In the warmest parts of the U. S., several varieties
can grow outside in regular soil with partial shade.
The best planting medium to use would be equal parts of
soil rich in organic matter mixed with perlite or pumice. Repot these plants in spring and summer.
During the summer, they need a lot of water; in the
winter, less is needed, unless of course we are going through a winter heat
wave, which is common in South Florida.
Do not let them dry out completely-the non-succulent species should be
allowed to remain a bit moist.
In early spring, pruning can be done to thin out the
plant and restore their shape by cutting back the stray
vines.
Propagation of these plants from cuttings of young shoots
is easy. I just let them dry out
for a day after dipping them in Root Tone and place them in a pot with very
porous mix. This should preferably
be done in early spring also.
A word of advise as to nomenclature: do not let yourself be confused with
those plants in the genus Cyphostemma, also in the Family Vitaceae. For years this latter genus has been
interchangeably used with the genus Cissus. I am sure that you have heard of the
pachycaul, Cissus jutae-well, it is NOT that but it is Cyphostemma
jutae. Be careful.
Aloe Polyphylla
by Sue Haffner
From Cactus Corner
News
Aloe polyphylla, the spiral aloe, is one of those fantastic plants
that make you want to rub your eyes. Is it real? A specimen plant, showing its
spiral growth pattern, is truly awe-inspiring.
It is also one of the world’s most endangered plants. Aloe
polyphylla (the name means “many leaves”) is native to basaltic mountain
areas of Lesotho, a small country entirely surrounded by South Africa. Plants
cling to high altitude slopes which are characterized by copious rainwater
runoff and snow in the winter. This habitat is under severe pressure from
farming operations, and the plant’s only pollinator, the Malachite Sunbird, is
also endangered. In addition to all this, Aloe polyphylla has been
over-collected for years. Travelers have mentioned seeing local people selling
plants along the roadsides or in markets. These collected plants have virtually
no chance of being re-established in cultivation.
Fortunately, nurserymen have been propagating Aloe polyphylla from
seed for years, and small plants are available in the trade at reasonable
prices.
The young plants resemble some other aloes, such as nobilis,
except that their leaves are noticeably softer and more “watery”. (Aloe
polyphylla is 95% water.) Plants must reach a diameter of at least 8”-12”
before they begin to spiral-and they may spiral either left or right-and amass
about 90 leaves in order to support production of the large
bloomstalk.
In our climate, Aloe polyphylla should be protected from hot
temperatures as much as possible. Most growth will occur during the cooler times
of spring and fall. The plant’s roots have a high oxygen requirement, and this
combination of temperature and water availability will keep the leaves firm. One
sign of a plant in distress is flaccid outer leaves lying on the soil
surface.
Alan Beverly is a Santa Cruz area grower who has specialized in Aloe
polyphylla for years. His firm is called Ecoscape. He recommends the
following container mix: to any good commercial mix add 50% by volume orchid
bark or 5/16” red lava or washed pumice. Be aware that, if you use bark, it will
disintegrate in two years and have to be replaced. Don’t be reluctant to put
small plants into large containers, as their roots appreciate the insulation and
the free root-run opportunity. In the ground, the plants will develop best in
sandy loam supplemented with organic material.
Propagation is by seed, though seed of this species is seldom available,
or by stem cuttings. Aloe polyphylla offsets only rarely. An article in
the May-June 1995 issue of Cactus and succulent journal described efforts
to pollinate this species. It also mentioned means employed by the Huntington to
get the plant to offset (e.g., cutting out the growing
point.)
Alan Beverly considers Fusarium crown rot to be the plant’s most serious
disease. This is characterized by wet purple lesions on the leaves, and can be
treated with Benomyl or other fungicides.
While the cooler summers of Santa Cruz produce better growing conditions
for Aloe polyphylla than does our hot Valley, you can still grow nice
plants if you cater a bit to their needs.
When Bad Things Happen To Good
Cacti
by Sue Haffner
From Cactus Corner
News
What’s this? Your favorite Rebutia has developed a pin-head? Your Lobivia
looks like a belt is cinching its waist? What’s going
on?
It’s so disappointing to find your favorite plants producing abnormal
growth. The usual reason for “pin-headedness”-etiolation-is that the plants were
grown in too much shade and/or watered too much. Sometimes, though, etiolation
can occur in plants that are in a well-lighted situation. One plant can
etiolate, while the one next to it looks fine. The speculation is that the
etiolated plant got off to a too-rapid start in the spring. Also, some genera
may be more prone to this behavior than others.
Characteristics of an etiolated plant are these: a thinner growing point,
an increased distance between nodes or tubercules, a paler color of the stem, a
“stretched” appearance.
Sometimes a short, columnar cactus will have a narrow area about the
middle of the stem. This “waist” ruins the appearance of the plant. It is
usually assumed that this indicates a change in culture in the plant’s history.
Etiolation might have begun, then normal growth resumed. Whatever the cause,
cells collapsed and this constricted area will never “plump out” again. One
friend had a Mammillaria with such a narrow waist that he had had to devise a
kind of crutch to hold up the plant’s head, its narrow middle now too weak to
hold it upright.
Another ugly condition that can overtake your plants is a corky, brown
epidermis that seems to creep up the plant from the soil line. The experts can’t
agree on what causes this. Some genera, such as Notocactus, seem more
susceptible to this than others. Even plants in habitat can display this
condition.
Aside from being philosophical about it, what can you do to return these
misshapen plants to a more normal condition? Well, get out a sharp knife. You
can declare, along with the Red Queen from “Alice in Wonderland”-Off with her
head!
Take off the etiolated top of the plant and discard it. Offsets will grow
from the old stump and can be removed from it to root on their own. For a plant
with a waist, the top can be taken off and put down to root. Be sure and let the
cuts dry before putting the plant in a rooting medium. For good measure, also
clean your knife with rubbing alcohol or a bleach solution when you move from
one plant to another.
The pictures below are from Cactus & succulent journal,
March-April, 1988.
Is It a Succulent? or Is It a Cactus?
by Lou Kilbert
Spinal Column, Michigan C&S
The word “succulent” is a general term that applies to
many plants that are often totally unrelated except for in the far, far distant
past! All cacti are more or less succulents - but most succulents are not cacti.
In the beginner’s mind, “cactus” is often applied to any spiny plant; although,
why beginners don’t then call roses “cacti” is beyond me! On
the other hand,
beginners often classify any fat plant without spines as a “succulent”. This
brief article attempts to clarify the issue for the beginning
enthusiast.
The name “cactus” is applied to a plant family, thus the
“cactus family”, just like the lily family or the rhododendron family, etc.
Cacti are plants that are exclusively American. Before the European expeditions
to the “New World”, there were no cacti in the “Old World”. Today, because of
mankind’s intervention, cacti are found on all continents and almost every major
island. Cacti are subdivided into three subfamilies: the Pereskiae, the Opuntiae
and the Cereae. The Opuntiads comprise the largest subfamily of cacti. Most are
easily recognized by the “Bunny Ears” growth habit that most assume. Opuntiads
are found from the tip of South America on Tierra del Fuego to the Yukon
Valley of North America. The two Michigan native cacti are both Opuntiads: the
Michigan Prickly Pear (Opuntia compressa) found throughout the lower peninsula
wherever the soil type and microclimate are favorable and a little known, very
hardy and attractive species from
the Porcupine Mountains of the upper
peninsula (Opuntia fragilis). The pads on that cactus are more or less rounded
to almost globular rather than having the more typical “mitten” shape. Opuntiads
are identified by:1) The fact that, when in active growth, true leaves are
present. These are the little green cylinders at the growing tip. They usually
fall off as the pad matures. The pad (mitten) is actually a flattened stem and
not a thickened leaf as beginners often assume.
2) The second characteristic that all Opuntiads have is
the presence of “glochids” or
microscopic, hooked spines. These are not the easily seen large spines that many
Opuntiads also have but the furry looking buttons that stud the surface of the
pad. These are the things that make many enthusiasts steer clear of this
subfamily. These tiny glochids seem to jump off the plant and attack you when
you least expect it. To remove
them, try pressing tape against the skin and
then rapidly pull the tape off. You can also apply white milk glue (Elmer’s
Glue), allow it to dry and pull it off along with many of the glochids. I have
even used a razor to shave off the part that sticks out of the skin; you will
still get a highly irritated reddened welt or ulcer from the embedded
hooks.
3) “Areoles” are a characteristic of all true cacti found
in all three subfamilies. These structures produce spines and flowers, and in
Opuntiads, the areole also produces the glochids and true leaves.
The
second largest subfamily of cacti, the Cereae, contains the plants that many of
us grow to love. Here you will find such a great variation in size, shape and
general appearance that beginners have difficulty finding the relationship
between them. This subfamily contains columnar plants and globular plants. In
general, the plants have ribs. Ribs allow a plant to expand to absorb large
quantities of water; at that time, the ribs may seem to disappear. When
“starved” for water, the ribs become more prominent. Areoles are found along the
outer edges of the ribs. Sometimes the ribs get further subdivided into
“nipples”, as in Mammillaria; each nipple is tipped with an areole.
Also
included in this subfamily are the Jungle Cacti: Christmas, Thanksgiving,
Easter, Rice and Orchid cacti. Except in the case of a few Rhipsalis (Rice
Cacti), the relationship of these cacti to others in the group is not easy to
see. If you ever grow one from seed and sometimes when they are grown under
stress (low light and high humidity), tiny stems resembling miniature columnar
cacti will be produced and then you may be able to see that these Jungle Cacti
are closely allied with the others in the subfamily.
The third subfamily,
Pereskiae, is not usually grown by hobbyists, but may be seen in botanical
gardens. These are “primitive” members of the family that look like thorny roses
that grew large enough to be called trees. The true leaves are large and waxy
looking. The flowers look like single roses. However, areoles are present and
produce the leaves, spines and flowers. And no, cacti did not originate in
prehistory from the rose family. Pereskias are grown throughout the tropics as
fruit trees. The fruit has the taste of a not-so-tart lemon.
Succulents
are plants that take up or absorb water very quickly and store it in special
water storage cells and organs. Succulents lose water very, very slowly 1)
because they have reduced their surface area to a minimum, 2) because they cover
their surface with waxy, water-resistant coatings and 3) because they greatly
reduce the number of stoma or breathing pores to a minimum. Notice this
descriptive definition doesn’t say anything about spiny-ness because succulents
may or may not have spiny appendages. Also notice that the definition is so
general that it applies to many totally unrelated plants in many
different
plant families.
Cultivation of succulents is based on this definition.
Succulents can take up too much water too quickly, mostly in cultivation. In
nature, abundant water just is not available to the plants. After taking up all
this excess water, because they lose water very, very slowly, they suffer and
may even die! They can’t get rid of excess water. They have
reduced stoma,
so water can’t be excreted through respiration. They have thick coatings on
their stems and leaves that won’t allow excess water to escape. Thus, one waters
carefully to prevent excess uptake. Christmas cactus suffer from “silver-skin
disease”; this is caused by over-watering; the excess water gets trapped between
the living green
tissue and the thick outer skin. When the water is
eventually eliminated, the skin appears silvery because now the layer between
the skin and the living tissue is filled with air. The shape with the greatest
volume and minimum surface area is a sphere. Many families have evolved species
that are more or less spherical in shape as an ideal adaptation to life in dry
climates. Look at pictures of Euphorbia obesa and Astrophytum asterias; two
totally unrelated plants with an almost identical appearance!
All cacti
are succulents. Other succulents often resemble cacti as a result of parallel
evolution. The family of plants most often mistaken for cacti are the Euphorbias
of Africa. The Euphorbia family is distributed worldwide in contrast to the
cacti that come exclusively from the Americas. Most of the Euphorbias outside
Africa are shrubs and
sub-shrubs and of little interest to collectors of
succulents. If spines are present, Euphorbias are easy to distinguish from
cacti. Euphorbia spines are branched, often with just two “horns”, but sometimes
having multiple branch points. Cactus spines are never branched; although, some
are delicately feathered. Also unlike cacti, the twin horned spines of
Euphorbias are mounted on a horny plate; this base plate often runs the
full
length of the rib, but may be just a little shield at the base of the
spine.
Euphorbias are filled with a milky sap that runs like white blood
from their wounds. The sap eventually clots into a rubbery latex. Euphorbias
were once investigated as a possible source of latex for the manufacture of
“rubber”, but that effort was abandoned. Caution! The milky sap of Euphorbias is
very acidic and can burn the eyes, mouth and sensitive
skin. Many people
develop an allergic reaction to the latex as well. Some cacti, especially
certain Mammillarias, also produce a milky latex; therefore, this is not a
foolproof distinguishing characteristic.
Along with Euphorbias, the most
often cultivated succulents come from the Lily and the Crassula or Jade Tree
families. Even though Agaves and Haworthias look totally different from the vast
majority of cactus, we still get people who ask, “Does that belong to the cactus
family?” In the general public’s mind “cactus” is indistinctly defined and the
word “succulent” is almost never used, even though that is the simple, broadly
encompassing term. I guess it’s up to us to keep explaining to people the
meaning of these words.
Quizzical Plants: Monstrose and Crested Succulents
by L. M. Moe
The Cactus Patch, Bakersfield, CA
To understand what causes monstrose and crested succulents, a brief look at how plants grow is necessary. All plants grow in length by increasing the number of cells at the tips of shoots and roots. These regions of active cell division are called apical meristems and this growth is called primary growth. Some plants, most notably the monocots (grasses, lilies, aloes), have meristems (called intercalary meristems) at leaf bases that cause leaf elongation. (This is why grass leaves continue to grow after they have been mowed). In woody plants there are additional meristems called lateral meristems that produce secondary growth. The most important lateral meristem is the vascular cambium, which produces wood and bark. Monstrose and crested growth only involves primary growth.
Cell divisions in the apical and intercalary meristems are highly regulated and finely tuned in each kind of plant, resulting in distinctive stem and leaf shapes. For example, very rapid apical growth with a suppression of branching (called apical dominance) results in long, slender stems whereas, slower growth results in "fatter" stems. Stems without apical dominance are highly branched. In general, cacti have apical dominance with slow apical growth and are "fat" (and the cells filled with water, making them succulent). So, in cacti faster growth results in columnar cacti and slower growth results in barrel cacti. Occasionally something called a growth mutation happens that "messes up" these regulated and coordinated cell divisions in the primary meristems. The causes of these mutations range from injury to bacterial or viral diseases. The three most common types of growth mutation are crests, monstrose growth and variegation.
In crests the growth mutation changes the shape of the apical meristem.
Instead
of a single growth tip the area of active cell growth becomes a line,
resulting in fan-like or crested growth (see photos of crested Euphorbia
resinifera and crested Trichocereus).
Euphorbia (117kB)
Trichocereus (84kB)
In monstrose growth, the local apical dominance is lost and every growth tip tries to grow as if it were the dominant point, resulting in a "knobby" or "lumpy, jumbled" growth.
Variegation can be a topic for a future newsletter, if there is interest. Please let me know.
Cresting and monstrose growth is not unique to succulent plants. Crests are found in many genera of non-succulent plants, including conifers and many common garden plants.
Crests and monstrose plants are grown the same as normal plants of the same species except that crests and monstrose plants tend to be more sensitive. This is one of the many reasons they are often grown as grafts. Monstrose and crested plants flower and produce seed just as other plants do. However the growth mutations are not generally transmitted by seed so the best way to propagate these plants is by cuttings.
More photos of crested and monstrose succulents can be found in your club library or at
www.miles2go.com/crest.htm
Cuttings
by Dick Kohlschreiber
The Epi-Gram Palos Verdes, CA July
2003
This is a good time to make cuttings and to plant
cuttings. We have always
recommended planting your cuttings directly in your planting mix. Be sure to let the cuttings callous for
at least a week before you plant them.
Don’t put them into too large of a pot. For most cuttings, I like to use a 3 ¼
inch pot. Be sure to not water the
cuttings until you’re sure they have developed roots. Be sure to put a plant stake with the
cutting in case the name comes off the cutting.
This is also a good time to make cuttings on your
Schlumbergera (Christmas Cactus) or Rhipsalidopsis or Hatiora (the Easter
Cactus). I have really been having
good luck by taking a Schlumbergera
cutting and dividing it into individual segments or joints. I let these joints callous for at least
a week and then plant them in pots of vermiculite. I like to keep the vermiculite moist and
in a short time, you’ll have roots on each segment. I’ll bring some of these to the next
meeting. Your Schlumbergera plants
should be showing new growth now and if they don’t, you may have root
problems. If your plant is wilting
at all, the roots are bad. Don’t
water these plants because that just makes the root situation worse.
If you have a Schlumbergera plant that is growing nicely,
don’t be in a hurry to plant it in a larger pot. They seem to do better if they are
crowded. If I have a plant that is
doing well in a 3 ¼ inch pot, I’ll move it up to a 4 inch pot before I put it in
a 5 or 6 inch pot.
If you live in an area where it really gets hot, keep the
Schlumbergera in a cool shaded area.
They do not like really hot weather.
I have had a lot of flowers on the Easter Cactus and very
often after the bloom, they fall apart.
You can plant the joints that fall off if you don’t let them dry out too
much.
Photos from Minas Gerais, Brazil by Nels Christianson Sunset Succulent
Society
(Please include entire caption line when using photos.
Thanks!)
#82 (800kBytes)
Cipocereus minensis in fruit, near Serro, Minas
Gerais Photo by Nels Christianson
Sunset Succulent Society
In Defense of Dactylopsis
For connoisseurs of the succulent Aizoaceae, or
"mesembs," there are several compellingly odd, but
difficult to cultivate species and genera that have taken on an
almost mythical quality. These vegetable Maltese Falcons include
Muiria hortenseae, Conophytum burgeri and
Didymaotus lapidiformis, but surely the strangest and most
horticulturally recalcitrant of the bunch is Dactylopsis
digitata, the finger mesemb. So, it came as something of a
shock to the community of succulent-plant enthusiasts when
Dactylopsis was subsumed into Phyllobolus
(Gerbaulet, 1997). Many of us never did quite get around to
changing our labels to Phyllobolus digitatus, though, and
in this article I will defend the continued use of
Dactylopsis, on grounds other than that of simple
inertia. Before getting into my defense of Dactylopsis, I
should summarize the arguments that were used to justify the
transfer to Phyllobolus. The reasoning was based on the
discipline of cladistics, which is a method of discovering
relationships among organisms, and reconstructing evolutionary
trees (cladograms). In cladistics, species are grouped together
if they have synapomorphies, which are shared derived
characteristics not present in other, putatively related groups.
One goal of a cladistic analysis is to find
"monophyletic" groups – groups of species that include
all of the descendants of a common ancestor, and exclude
representatives from all other evolutionary lineages. It is the
overwhelming consensus among modern biologists that cladistics is
the best way to determine the evolutionary history of living
things, and that classification schemes should only recognize
taxa that are monophyletic. No-one, including Gerbaulet, contests the idea that
Dactylopsis is a monophyletic entity. Depending upon whom
you talk to, the group contains either two species (D.
digitata, the large-leaved southern form, and D.
littlewoodii, the small-leaved northern form)(van Jaarsveld
and Pienaar, 2000), or a single, variable species (Gerbaulet,
2001). The two forms are mainly distinguished by size, and share
synapomorphies not seen in any other genus in their subfamily
(the Mesembryanthemoideae): large, hyper-succulent cylindrical
leaves, and tiny white flowers with filamentous petals that tend
to keep their form as they dry out. The reason why
Dactylopsis was sunk by Gerbaulet is that she claimed that
it had other synapomorphies in common with Phyllobolus, in
particular the dwarf, tuberous relatives of P. resurgens.
Although Gerbaulet did not present a formal cladistic analysis,
she contended that Dactylopsis was nested within the
evolutionary branch (clade) containing P. resurgens, and
thus that Phyllobolus would not be a monophyletic genus if
Dactylopsis was maintained as a separate entity
(Gerbaulet, 1997). Based upon gross morphology, it is difficult to see what
characters could possibly link Dactylopsis to
Phyllobolus: the succulent, persistent green stems, smooth
seeds, and smooth, waxy leaves of Dactylopsis contrast
strongly with the ephemeral stems, rough seeds and warty,
bladder-cell covered leaves of the P. resurgens group.
The strength of Gerbaulet’s (1997) argument lies instead with
anatomical characteristics. The stems and roots of
Dactylopsis, and the tubers of geophytic
Phyllobolus species, thicken via the production of
successive rings of vascular tissue that consists mostly of
spongy, water-storing parenchyma cells. These organs also become
covered by a well-developed periderm (an outer layer of
protective cork cells) in both genera. However, the status of
these characters as synapomorphies unique to these two genera is
dubious. All perennial Mesembryanthemoideae that I have examined
thicken their stems and roots via successive cambia giving rise
to concentric rings of vascular tissue, which tends to be mostly
parenchyma in organs that do not need to support themselves
mechanically, such as the stems of a cushion plant like
Dactylopsis or the subterranean tubers of
Phyllobolus. A periderm, too, seems to be developed to a
greater or lesser extent in all of the genera of perennial
mesembs that show secondary thickening growth in roots or stems.
I would suggest that the anatomical characters used to sink
Dactylopsis into Phyllobolus are not synapomorphies
of these genera at all, but ancestral characters
(symplesiomorphies) present in a wide variety of genera in the
subfamily, and thus uninformative for determining evolutionary
relationships. If the link between Dactylopsis and
Phyllobolus is tenuous, what are the closest relatives
(sister groups) to Dactylopsis? The extreme morphological
reduction of dwarf succulents like Dactylopsis can make
the task of identifying synapomorphies difficult. However, I
have found several characters that indicate a strong link to
Aspazoma, an obscure, monotypic genus of small shrubs
(Opel, 2002). A relationship between Dactylopsis and
Aspazoma was first suggested almost half a century ago by
Schwantes (1957), who placed both genera in the same
subtribe. The most suggestive characteristics linking
Dactylopsis and Aspazoma involve the structure of
the leaves. In both genera, the epidermal bladder cells that are
present in most Mesembryanthemoideae have been lost, and the
leaves are quite smooth and waxy. Both genera have sheathing
leaf bases that surround the stem, a character that does not
occur in any other genus in the subfamily. Moreover, the
function of the sheathing leaf bases is the same in both genera:
the leaves dry up to form a protective tunic that covers the
succulent stems during the summer dormant period. This mode of
dormancy is unique in the family Aizoaceae, though many genera
(e.g. Conophytum) show an analogous strategy, in which
succulent leaves (rather than stems) are protected by a papery
tunic of old leaves during the dry season. Another character that suggests that Dactylopsis is
related to Aspazoma, and not Phyllobolus, is their
succulent stems, which have a layer of green chlorenchyma in
their cortex, and prominent bladder cells on their epidermis.
The stems remain succulent for two growing seasons, and then lose
their green cortex and develop a periderm. Nothing similar is
known from Phyllobolus, though the same type of stem
morphology and development occurs in the genera that are commonly
considered to be related to Aspazoma: Psilocaulon
and Brownanthus (secondary growth in the stems of these
shrubby genera is woody, consisting mainly of fibers and
tracheids, whereas the cambia of Dactylopsis mostly
produce soft parenchyma). In addition, Dactylopsis and
Aspazoma both have smooth-coated seeds, while seed coats
in Phyllobolus tend to be rough. In terms of overall
shape, the elongated pyriform seeds of Dactylopsis have
little in common with either the robust, D-shaped seeds of
Phyllobolus or the large, flattened seeds of
Aspazoma. Given the available morphological evidence, it seems most
reasonable to maintain Dactylopsis as a separate genus,
closely related to Aspazoma, but easily distinguished by
its extreme succulence and unusual floral structure. Further
research is required to determine how the hypothesized
Dactylopsis/Aspazoma clade falls out with respect
to other allied genera, such as Brownanthus, and it is
probably safe to assume that more rearrangements will need to be
made before the taxonomy of this group settles into a stable
state. Gerbaulet, M. 1997. Revision of the genus
Phyllobolus N.E.Br. (Aizoaceae). Bot. Jahrb. Syst.
119: 145-211. Gerbaulet, M. 2001. Phyllobolus. In: H.E.K.
Hartmann, ed. Illustrated Handbook of Succulent Plants:
Aizoaceae F-Z. Springer-Verlag, Berlin. Opel, M.R. 2002. Aspazoma in the veld and under
glass. Mesemb Study Group Bulletin 17: 59-60. Schwantes, G. 1957. Flowering Stones and Mid-day Flowers. Benn, London. van Jaarsveld, E.J. and de Villiers Pienaar, U. 2000. Vygies: Gems of the Veld. Cactus & Co. Libri, Venegono, Italy.
#84 (800kBytes)
Discocactus placentiformus growing in quartz sand,
south of Diamantina,
Minas Gerais Photo by Nels Christianson
Sunset Succulent Society
By Matthew R. Opel
Dept. Ecology and Evolutionary
Biology, University of Connecticut, Storrs, CT 06269
email:
matthew.opel (at) uconn.edu
San Francisco Succulent and Cactus Society Newsletter