CACTUS

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What are cactus? For one thing, they are "Succulents".

What are Succulents?

Succulents are plants that have organs such as leaves, stems or roots that are capable of storing water during the rainy or wet season in order to survive extended periods of drought. All the plants in the cactus family (Opuntiacea = Cactacea) are considered stem succulents. During periods of moisture, the stem swells and then during droughts slowly contracts. Cactus that have ribs are particularly well adapted to this as the ribs fill in and contract like an accordion

Have you noticed that cactus have no leaves. What they usually, but not always, have is spines which can stick and hurt. The word Cactus comes from the Greek word "Kaktos" which means thistle. Actually the spines are highly modified leaf or leaf parts. Normally leaves are rather poor at conserving the water supply of a pant. Most plants also cannot stand high temperatures. Therefore the inability to store water and the intolerance of high temperature in dry hot locals makes life for many plants impossible.

The leaves of most plants are very good at photosynthesis, which means taking sun light to make food out of the other supplies brought up to the leaves by the roots, trunk, stem and other parts of the vascular system between the plants root to the leaves. Leaves also can cool a plant off.

Since cactus have no leaves, the epidermis, i.e. the skin under the thorns, is green and operates as a photosynthesis organ for the cactus. Instead of a cooling system, like leaves, cactus have developed a tolerance for heat and therefore get by without the cooling system of leaves.

Cactus are not the only succulent with spines. However, cactus have a grouping of spines on the areoles (which is a radial grouping of spines on pad like buds where the flowers and shoots may grow from the cactus). It is this feature which helps distinguish cactus from other succulents. The areoles are usually arranged in a regular pattern which may be along ribs on the cactus or on the barrel of the cactus. The are often in equally spaces intervals over the face of the pad like cactus.

A family of plants which often appear like cactus is the euphorbia family (Euphorbiacea) which contains such plants as Cow's Horn Cactus (Euphorbia grandicornis), African Milk Bush (E. trigona) and Crown of Thorns (E. milii). You can tell the difference between members of the cactus family and members of the Euphorbiacea family by making a small cut. Cactus sap is clear and watery, whereas Euphorbiacea is white milky sticky sap. Euphorbiacea have no leaves to a few and have just green stems, but they do not have areoles. A Pencil Plant is a good example. Cut it and it bleeds profusely a white sticky milky type liquid.

To help identify cactus, some books group them by form. These include:

In some cactus, the areoles are hard to find, as they are grouped along the tips or edges of the stem segments and are very small. The Christmas cactus (Schlumbergera sp) is an example.

You can own one of the
400 signed limited edition eArt prints
of each of these beautiful cactii

Click here

These are eArt Scans of real live Cactii.
They are not photographs, but the live Cactii
scanned directly into the computer by Dr. Proctor
using his eArt Scanning technique

Prickly Pear Cactus
on Lavender Background
Item #		 Prickly Pear Cactus with
Chrysanthemums, Begonias
and an unknown wild flower
On Gold Background
Item #		 Prickly Pear Cactus with
Bougainvillea and an
unknown wild flower
on Gold Background
Item #
Prickly Pear Cactus with
Begonias, Bougainvillea and
an Unknown Flower,
Grape Leaves & Lizard
Item #		 Prickly Pear Cactus
with multiple Yellow Flowers
on Scarlet Background
Item #		 Prickly Pear Cactus
with multiple Yellow Flowers
on Light Green Background
Item #
Prickly Pear Cactus
with multiple Yellow Flowers
on Lavender Background
Item #		 Prickly Pear Cactus
with National Flower
of Argentina
on Yellow Background
Item #		 Prickly Pear Cactus with
Chrysanthemums, Begonias
and Unknown Flower
on Gold Background
Item #
Prickly Pear Cactus
with Chrysanthemums and
Tuberous Begonias and
Unknown Flower on
Light Green Background
Item #		 Prickly Pear Cactus
and Bougainvillea and
Unknown Flower-Version #1
on Mixed Background
Item #		 Prickly Pear Cactus with
Begonias, Bougainvillea and
an Unknown Flower
on Beige Background
Item #
Prickly Pear Cactus
and Bougainvillea and
Unknown Flower-Version #2
on Mixed Background
Item #		 Prickly Pear Cactus
with Primroses and
Wild Bergamont
on Yellow Background
Item #		 Prickly Pear Cactus
with solo Yellow Blossom
on Lavender Background
Item #
Prickly Pear Cactus
with solo Yellow Blossom
on solid Orange Background
Item #		 Prickly Pear Cactus
with solo Yellow Blossom
on mixed Orange Background
Item #		 Prickly Pear Cactus
with solo Yellow Blossom
on Scarlet Background
Item #
Prickly Pear Cactus
with National Flower
of Argentina
on Orange Background
Item #		 Prickly Pear Cactus
which grew in heart
shape with two Flowers
on Dark Purple Background
Item #		 Prickly Pear Cactus
which grew in heart
shape with two Flowers
on Turquoise Background
Item #
Prickly Pear Cactus
which grew in heart
shape with two Flowers
on Orange Background
Item #

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