What is a Cactus?
Evolution and Phylogeny
(cf. Zygomorphic) Radially symmetrical. A term used in botany to describe. flowers which are symmetrical about their longitudinal axes, e.g. Schlumbergera x buckleyi. They have no particular "plane of symmetry". Any longitudinal slice along the central axis produces similar halves of the flower.
(cf. Gynoecium) The collective name of the male part of a flower, i.e.the group of stamens which produce pollen. It includes parts of the flower that are derived from stamens, e.g. staminodes (sterile stamens) and petaloids (each with a rudimentary anther).
The specifically male part(s) of a flower and the source of pollen, each anther is situated on top of a filament, often in a position where it may efficiently transfer pollen to pollinators such as bees, bats, etc. or to pollinate its own gynoecium. It is attached to the filament in one of three ways; i.e. it is innate (also said basifixed), attached by its base at the apex of the filament; or adnate, attached for its full length to the top side of the filament; or it is versatile, attached by its back centre to the very tip of the filament.
The opening of a flower.
(cf. Betacyanin) Two Flavonoids, the pigments called Anthocyanins (reds and blues) and Flavones (some yellows), play no part in the coloration of the fruit or flowers of families of the order Caryophyllales (and Cactales, where considered a separate order.). They are, however, the pigments of other xerophytes, the "other Succulents" of interest to succulentophiles.
(cf. Vegetative Propagation) One of the five modes of asexual propagation of plants; this mode, by germination of apomictic seed, is similar to parthenogenesis, each seed resulting in a clone of genetically identical plants. Apomixis is seldom used in the propagation of cacti and other succulents.
In cacti, this form of the name is given to the Spine Cushions situated in the axils of leaves, e.g. of Pereskia and, in all other cacti, on the ribs, on the tubercles or between tubercles. By definition, Areoles are characteristic of all cacti. Their hair, bristles, spines and glochids are the ultimately sublimated branches, shoots and leaves of the ancestors of all cacti, evolved by slow, gradual adaptation to the changing climates which they survived. Note that Areole is the specific word form for use with cacti, and its meaning is different from that of "Areola: = The small spaces between lines on a surface, e.g. of a leaf or an insect wing, etc.". As well, Anatomy defines it as "a...pigmented area... surrounding a nipple Both of these forms are diminutives of the Latin area = space.
In cacti, a bud developed in the position analogous to the primitive axil of a leaf (cf. Pereskia) on the upper edge of the areole or between tubercles, is called an Axillary Bud". It is the structure which may differentiate into a flower, a shoot, a branch, or an offset. In cacti, the bud is situated usually in the areole's axis, i.e. on the upper side. In most ribbed cacti, e.g. Neolloydia, the bud is on the upper edge of the elongated areole. In Thelocactus it has moved farther up on the areole's end in a short furrow, while in Coryphantha, the furrow may extend almost to the base of the tubercle, and the bud is there. In Mammillaria the furrow has disappeared but the bud has moved to the tubercle's base, the axil between adjacent tubercles, where the flowers, fruit and sometimes bristles or hair, are produced. This interesting topic is discussed in detail in Lyman Benson's The Cacti of the United States and Canada.
(cf. Axillary Bud); From Latin axilla = armpit, this refers to the upper angle between a leaf petiole and the stem. Axillary buds, hairs, bristles, side shoots or flowers are usually produced from the axils. In Mammillaria, the region at the base of and between the tubercles remains axillary; the shoots, offsets, flowers and tufts of hair are produced there.
A common English vernacular name denoting species of Echinocactus or Ferocactus.
A fruit with soft, fleshy pericarp containing hard seeds, derived from a compound (syncarpous) pistil; e.g., Mammillaria.
(cf. Anthocyanin) Nitrogenous dyes which provide the colours of cacti and other families of the order Caryophyllales (and the order Cactales where considered separate.). The presence of Betacyanin is one of the defining characters of these families including; Aizoaceae,
Cactaceae, Chenopodiaceae, Phytolaccaceae and Mesembryanthemaceae.
(cf. Vername) A convenient, abbreviation of "Botanical Name" adopted for purposes of the compiler of "The Cross Reference Index of Botanical and Vernacular Names of Cacti and Other Succulents" used in the Dalhousie Cactus Collection Website. It refers to the latinized names of plants as he has found them, whether or not recognized by the International Convention on Botanical Nomenclature (ICBN), together with their meanings and other data, where possible.
A modified or reduced leaf usually associated with inflorescences, sometimes serving to emphasize the flowers; e.g. the red bracts of Poinsettias. Shoots and flowers may arise from a leaf axil but a flower arises more often in the axil of a bract.
(cf. Spine, Glochid) In cacti and other succulents, the word bristle refers to the smallest, very short hairs and/or rudimentary spines, found on many succulent plants and, e.g. sparsely, in the areoles of some epiphytes. They are not to be confused with glochids also stiff and small but very sharp and barbed spines that are characteristic only of the subfamily, Opuntioideae, of the family Cactaceae.
(cf. Deciduous). From the latin word caducus = falling, this adjective pertains to plant parts that normally fall off early, such as the evanescent (fugacious) leaves characteristic of opuntiads, and short-lived bracts on the peduncles of Echeveria inflorescences for example. Parts which die or fall off at maturity or fall at a particular time or in certain conditions are termed deciduous.
(cf. Corolla) Collectively the sepals, the floral cup, the outermost whorl of the floral parts. Together with the petals, they form the perianth which serves to protect, support, or nourish the flower, but often also they are coloured, or otherwise adapted, to attract pollinators.
Is a word derived from the Greek word karpos = fruit. Carpels comprise the innermost part, the female organ (gynoecium), of a flower. A carpel may be a single pistil or part of a compound pistil. Its base forms the ovary, containing the ovules. The ovary, when pollinated, and the ovules successfully fertilized, culminates in a fruit.
Derived from the Latin word caudex = tree, this word and its forms are used to describe succulent plants characterized by swollen stems or stem bases at or below ground level. Some examples are; Beaucarnea (Nolina), Dioscorea, and some Othonna. Most caudiciform plants are succulent xerophytes which survive their dormant and semi-dormant seasons by sloughing off their top growth and sometimes their roots, and protecting their dormant parts in characteristic ways. Their wide acceptance as adjuncts to Cactus and Other Succulent Collections has burgeoned strongly only in the last quarter of a century or so.
Is derived from the Latin word kaulos = stem and Karpos = fruit. The Oxford Dictionary lists its first use by Gray, in his 1880 text-book of Botany, as "...applied to plants which live to flower and fructify more than once or indefinitely." This is the sense in which it is used in the list of the seven defining characteristics of cacti.
(q.v. Vegetative Propagation) This word, derived from Greek word klon = twig, is used to define all of the asexual, i.e. vegetatively propagated, descendants (ramets), considered together, of a particular ancestral seedling plant (the ortet) which are all therefore genetically identical to that ancestor. Certain clones may be desirable because of special features such as very dependably producing flowers and fruit with very uniform characters even when grown in very diverse environments. The size of the plants and/or of the leaves may be quite variable under different conditions however, and some further mutation is not entirely precluded. There are five basic ways of producing plants asexually, listed below under vegetative propagation.
(cf. Parallelism, Divergence,). Convergent Evolution, also called homoplasty, refers to the similarity between plants of two or more distinctly different phyletic lines which have developed similar characters because of their evolution in and adaptation to similar but unconnected environments, or through similar reproductive factors. For example; some species of the succulent Euphorbias of Africa and Cacti of the Americas are remarkably similar in general appearance due to their evolution in very similar habitats and climates.
(cf. Calyx) (Latin corolla = little crown). The usually colourful assembly of the petals and petaloids of a flower. Together with the Calyx, it forms the perianth (q.v.).
A form of monstrosity; abnormal plant growth reminiscent of a crest, or a convoluted ridge, e.g. Sinocrassula yunnanensis f.cristata Cristate Chinese Jade, See Photo CS173.2 in the data base. Its cause is not well understood.
The relatively thick, waxy membrane of some succulents, almost impermeable to water, covering the cells of the epidermis, especially of cacti and most evident on Epiphytic cacti.
(cf. Platyopuntia) A subgenus of Opuntia referring to those plants with cylindroid or terete stems.
A determinate inflorescence in which a single flower terminates the main axis, and which opens before any lateral or subsequent flowers do so. A bract on a cyme may have, in its axil, a flower or a branchlet or it may wither. In a monochasial or helicoid cyme, the terminal flower, on its pedicel, originates from the axil of one of a pair of opposite bracts. A new branchlet, with a pair of bracts continues from the axil of the other bract of the pair. And this sequence continues. A scorpioid cyme results when single, alternate bracts form spirally in sequence along the axis, usually at 120 degrees from each other, with or without a nodal space between, and a new flower on its pedicel originates in the axil of each. Subsequent single bracts continue the inflorescence. A compound cyme results when opposite bracts both form one or more branchlets repeatedly, each with a terminal flower, resulting in a flower cluster in which the florets bloom in sequence from the oldest flower, at the center, toward the youngest at the edges. A more elaborate continuation of the theme of the helicoid cyme, so to speak.
(cf. Monocotyledon) A flowering plant having two cotyledons (seed leaves) in the embryo. All cacti and most 'Other Succulents' are dicotyledons.
("Two forms") Said of a plant which demonstrates two distinct forms; e.g. of leaf or of stem. See, for example, the discussion of the two forms, the juvenile and the adult, of the phylloclades of Rhipsalidopsis rosea, the Rose Easter Cactus, in 'Paul's Notes'.
(cf. Convergence, Parallelism, Divergency) This word comes from the Latin word divergere = to separate. Some members of a population of species, in the course of gradual variation (mutation) eventually may diverge enough from the norm as to become less and less able to interbreed with the unchanged or differently changed members, and so may become a completely distinct species.
(cf. Fibonacci Series) In this form, the word refers, in one Dictionary of Scientific Terms, as the "fraction of a stem circumference, usually constant for a species, which separates two consecutive leaves in a spiral". This implies that both the angular separation and the axial distance (nodes) between two leaves are included in this form of the term.
(cf. Hypogynous, Perigynous) Having the floral cup or tube (hypanthium) attached near the top of the ovary. The ovary is 'inferior'; i.e. attached below the insertion of the flower parts. (q.v. Inferior Ovary).
("upon plants") Growing on other plants but not parasitic on them e.g. Epiphyllum, Schlumbergera, Rhipsalidopsis, etc.
Adopted from the French word etioler = to blanch, this word describes a plant that is pale and weak, with less than healthy, extended growth, due to poor or insufficient light, nutritious conditions, or disease.
A taxonomic unit lying between the higher rank of Order and the lower rank of Genus. It is composed of a group of related genera, with a few exceptions, e.g. Compositae, Leguminosae, etc., The names of plant families usually end with '-aceae'.
A numerical series in which each number is the sum of the two preceding numbers; e.g. 0,1,1,2,3,5,8,13, etc. In plants, it arises; e.g. in the habit of new growth, at certain angular separations (cf. Divergency), usually spirally, around a stem or floral axis. The higher number of each pair is the count of the number of sprouts in one stem circumference, the other number is an artifact of the sequence of the growths. In Cactaceae, it is particularly visible in the disposition of the areoles when viewed from above the plant, e.g., some Mammillaria, especially visible in M. mystax, and some Rebutia. It was named in honour of Leonardo Fibonacci, the outstanding mathematician of the middle ages, ca.1200AD, who first studied and described it.
The "stalk" of a stamen. Together, the filament, and the anther that it supports, comprise the stamen.
An infraspecific rank below variety. It is the smallest category recognized in botanical classification. It is used to denote sporadic or minor, random differences in morphological features of plants, mainly in horticultural applications.
(pl. Genera); A group including one or several related species that are clearly separate from, and do not normally interbreed with, plants of other genera.
An adjective used to describe the powdery, greyish or bluish, waxy coating or bloom found on some echeverias, grapes many Mesembryanthemaceae and Crassulaceae for example.
(cf. Bristle) One of the minute, barbed, specialized spines occurring in the areoles, and a defining characteristic, of opuntiads (Chollas and Prickly Pears). Unlike the larger spines in the areoles, glochids are strongly barbed and take their name from the Latin word glochidium = a barbed hair of a plant.
(cf. Androecium) The collective name of the female, innermost parts of a flower comprising the carpels which may be single or compound pistils enclosing the ovary and the ovules.
(cf. Hydrophyte, Mesophyte, Xerophyte); Plants which thrive in, or tolerate, salt water in their growing media. Salicornea europaea, the Glasswort or Samphire of boggy salt water beach rims, is a halophyte that resembles many succulent plants in form and habit.
refers to the habit of parts of a plant, e.g. leaves and hence axils, to arise successively in a helix around the stem of a plant or the axis of an inflorescence. The term Fibonacci Series has a particular relevance to this factor.
In biology this term refers to plants which bear differing forms of some of their parts; e.g.leaves, stems, etc. on the same plant. A good example is Rhipsalidopsis rosea Rose Easter Cactus. Refer to the article on this topic in the 'Paul's Notes' Section.
Refers to plants which bear different forms of their leaves on the same plant. Cheiridopsis candidisissima the Victory Plant, for example. See Photo CC014.0 in the Data Base.
(cf. Convergence) From the Greek words homos = same and plastos = moulded, this word is a more formal name for 'convergent evolution' or 'convergence' in that sense. The words 'homoplasy' and 'isotely' also describe the same phenomenon.
(cf. Apomixis, Vegetative Reproduction). Any cross-breeding, the sexual mating of parents of different but compatible species of animals or plants, produces hybrids.
(cf. Halophyte, Mesophyte, Xerophyte); Aquatic plants; ones that require constant , if not copious, moisture in which to grow. None are of much interest to Succulentophiles per se.
(cf. Epigynous, Perigynous) From the Greek hypo = below and gyne = female, this word refers to the position below the gynoecium; e.g. a hypogynous perianth is inserted (grows from) below the gynoecium. Graptopetalum paraguayense is one example. See the Paul's Note entitled "A Ballet of the Stamens".
Overlapped, like bricks in a wall, the scales of a pine cone or the leaves of an Echeveria. Many succulent plants have 'rosettes' of imbricated leaves, an important factor in the protection of a plant from excessive light and water loss.
A vernacular translation of the botanical term epigynous, applied when stamens and perianth are attached to the top wall of the ovary, but below the base of the pistil(s).
"The unformed growing cellular tissue of the younger parts of plants" (Oxford Dict.); i.e. at the tip of growing stems or branches.
(cf. Halophyte, Hydrophyte, Xerophyte); From the Greek meso = middle, this word refers to plants that are intermediate between hydrophytes and xerophytes, i.e. plants which grow in soils containing moderate amounts of available moisture.
Annual and biennial plants which flower and fruit only once and then die, roots and all, or only the flowering and fruiting parts may be affected. These are monocarpic. Some long-living woody perennials may form offsets, e.g. Agave, before dying. These also are monocarpic. On the other hand, only the flowering parts of some woody perennials are monocarpic branches; e.g. Aeonium, do so while younger branches flower and die later. In Beaucarnea, over a period of many years, flowering terminates the growth of each aged branch and one or more monocarpic branches eventually sprout near the terminus. Sometimes new branches will form from the base of a group of doomed flowering stems, e.g. some Kalanchoe.
(cf. Dicotyledon); Plants having one cotyledon (seedleaf) in the embryo. Some 'other succulents' are monocots, e.g. Agave and Aloe.
(cf. cristate); An individual plant whose growth deviates considerably from the normal. Many of the abnormal forms are attractive to many collectors e.g. Opuntia fulgida fa. mammillata 'Boxing Glove' (cristate) and Lophocereus schottii 'Totem Pole' (monstrose, knobby).
External features; e.g. form, structure, general appearance, growth habit, etc.
The study of form; e.g. a plant's external characteristics and their variations.
(cf. Variation); Spontaneous or gradual variation of one or a few of the characteristics of a species or genus which may eventually lead to new forms of genera or species. Causes may be due to normal variation in normal sexual generation, or gradually through segregation to different environmental or generational influences.
The nectar-secreting glands or parts of a flower or plant. These, like colour, scent, and disposition, play a very important role in attracting pollinators but seldom are essential otherwise to the well-being of plants.
A new branch or stem or whole young rooted plant which develops from a larger stem or branch and which may drop of its own accord e.g. Echinopsis, or which may be separated to continue as an individual plant on its own roots. A particularly interesting case is presented by certain Kalanchoe plants, particularly K.daigremontiana (Mexican Hat, etc.) and K.tubifora (Chandelier Plant, etc.). Both these (and some other) species produce complete, minuscule, rooted plants in crenelations at the edges, or the tips, of their adult leaves. These eventually fall off and, taking root, continue to grow where they fell.
(cf. Ramet, Clone); The original, single seedling plant ancestor of a clone.
That enlarged part of the pistil which contains the ovules. It is the specifically female, reproductive gland of a flower's gynoecium which culminates as a fruit.
(cf. Divergence, Convergence): The descendents of a diverging phyletic line may at some point stop diverging and continue to evolve while retaining many similarities with their precedents.
(cf. Peduncle) The stalk from the rhachis to an individual flower or floret of an inflorescence.
(cf. Pedicel) The stem or stalk of an individual single, or cluster of, flowers or fruit, or of a simple or compound leaf
(cf. Annual, Biennial) Plants that live and flower for more than one year.
Formed from the Latin and Greek words for "around" and "flower", this word refers to the petals and sepals of a flower, specifically the corolla and calyx, considered collectively as a floral cup.
(cf. Epigynous, Hypogynous) Having the perianth (floral cup), including the stamens, inserted (growing from) around the gynoecium.
In most flowers, one of the usually highly coloured inner perianth parts, very attractive to insects.
(cf. Geotropism) The tendency of plants to turn their growing parts toward the more intense light, e.g. Notocactus leninghaussii stem summits are canted toward the sun or, at any rate, toward the strongest source of light.
(syn.Cladophyll, Cladode); From the Greek word phyllon, leaf and klados, sprout. This is the proper name of the round or flattened stems of epiphytic cacti which appear, but also function, as leaves.
The evolutionary history of a group of organisms. Recognized by finding series of common characteristics in the subject organisms and deducing their line of development.
The seed-bearing, female organ of a flower, consisting of ovary, style and stigma; together, they comprise the gynoecium, which may consist of one or several pistils.
A subgenus of Opuntia referring to those plants with flat, discoid stems.
A general term applied to the haploid (1n) pollen grains that develop in the Anther of a flower; they are the immature male sex cells occurring in the seed plant's reproductive cycle.
The transfer of pollen from its point of origin (anther) to a receptive surface (stigma).
(cf. Anther) The specialized, pollen-bearing structure of the Asclepiadaceae which is extracted by pollinators from a flower and transported for pollination of another flower.
The central axis of an inflorescence, e.g. of a floral spike or a raceme, and also the central axis of a compound leaf or a fern frond. From the point where a plant stem becomes, and then continues, as an inflorescence, compound leaf or a frond, it is so called.
(cf. Ortet); An individual plant member of a clone (q.v.).
In cacti and other succulents, these are distinct, individual parts of stems, like the pads of Platyopuntia, or the "joints" of a phylloclade, are termed segments.
One of the green, or usually not highly coloured, outer whorl parts (calyx) of the perianth of most flowers, as opposed to the usually more colourful petals.
(sing.= Seta) Bristle-like, minute spines, usually borne in loose clusters or close-set pads, e.g. in the areoles of most Opuntia, as opposed to the mat-like velvety skin fuzz of some echeverias and many stapeliads. They are not the same as the glochids also located in the areoles of opuntiads.
A taxon composed of a group of related varieties or a single unit; a living natural species, a reproducing population or a system of populations of closely related individuals.
A mutation which is considered valuable enough to perpetuate while retaining its valuable characteristics, which may not breed true sexually. It must therefore be propagated asexually.
A stamen usually comprises a filament and an anther, the latter connected to the filament either at its base (basifixed or adnate), at its midpoint (versatile), or it may be attached for its full length to the side of the filament (innate).
The terminal pollen-receptive part of the pistil of a flower, supported by the style which leads to the ovary; a solitary style may bear more than one stigma. In the cacti the style bears usually three or up to about twenty stigmata.
(pl. Stomata): One of the small breathing pores in a leaf or on the green stem of a succulent plant by which exchange of gases (water, carbon dioxide and oxygen) is accomplished.
A taxon of a rank between family and genus.
This refers to juicy or sappy tissue capable of storing large quantities of water and nutrients.
An adjective used to describe e.g. a segmented stem that is cylindrical and smooth without ridges or furrows. Because the word 'cylindrical' is too general a term, sausage- or cigar-like or slightly tapered stem segments are often so described.
Inhalation and exhalation of water vapour and gases through the stomata of the leaves or stems of plants. Cooling by evaporation.
A taxon of a rank between family and genus, but lower than sub-family.
A small, protuberance or hump; in the cacti, a stem protuberance bearing an areole. Mammillaria and Rebutia, for example, have tubercles, each with one areole at its summit, rather than ribs.
(cf. Mutation). A divergence in growth from the usual or normal, of one or a few of the characteristics of a species or a genus. Sometimes this different growth is inheritable by succeeding direct generations. Where the variation is not great, such 'varieties', when desirable, are often given 'cultivar' (cultivated variety) names and may become commercially or scientifically important. Where a species' variation is great or strongly different from the normal, and if it breeds true, it may be sufficiently mutated (a 'sport') to consider it as having become a new species.
There are five basic modes of propagating plants non-sexually. These are listed and described at length in most biology textbooks including, for example, Jules Janick's Horticultural Science> (Fourth Edition,
W.H.Freeman and Company, New York, 1986). Briefly, these modes are: 1. Use of apomictic seed (apomixis); 2. Sowing specialized, reproducing parts of plants such as: runners, rhizomes, tuberous roots, stem tubers (caudices), corms, bulbs, offshoots (often rooted); 3. Layering parts of a living plant until roots have formed, or cutting and treating parts for rooting separately; 4. Grafting, usually in special, not numerous cases; 5. Tissue Culture, a specialized, laboratory process. Modes 1 and 5 are rare in general applications for Cacti and Other Succulents. Modes 2 and 3 are common and universal, while mode 4 is semi-specialized, requiring some expertise and patience.
(cf. Botname) A convenient abbreviation of "Vernacular Name" adopted for purposes of the compiler of "The Cross Reference Index of Botanical And Vernacular Names of Cacti and Other Succullents" used in the Dalhousie Cactus Collection Website. It refers to the "Common Name" used in the vernacular of any language which, where possible, has been identified, with its meaning, in the reference.
From the Greek words xeros = dry and phyton = plant, this word refers to plants which grow in physiologically dry soils or locations and must therefore depend, for their moisture, upon some other source; e.g. mists, dews, etc.
(cf. Actinomorphic): Derived from Greek zygo = yoke. In botany; having only one plane of symmetry along which a flower can be divided into similar halves. Schlumbergera truncata is one example.
Return to Top