intricate crests much sought after by collectors. And when we reach those highly succulent, cactus-like euphorbias that range from India and southern Arabia through all of Africa to the Cape Province, we suddenly realize the immense wealth at our disposal
It is really amazing to see how closely these succulent euphorbias resemble cacti. Indeed, many of them have been given cactus names, as £, opuntioides, £, cereifnrmis, or £, mammillaris. Like the cacti, they are all stem succulents wiih more or Jess transient leaves. They range in size from tiny compressed plants an inch or two high, much like the Living Rocks, 10 great columnar and treelike species rising sixty feel or more resembling the giant Torch and Candelabra Cacti, This uncanny resemblance is one of ihe classic exanv pies of parallel development in the plant world. For under the same pressures of necessity two totally different plant families in widely separated continents have taken on strikingly similar forms in ihe process of adaptation to drought In every way the succulent euphorbias are to the Old World what cacti are to the New,
But while the novice may be confused at first by the outward similarities of these two plant families» there are a number of clear-cut differences which will help him identify the euphorbias. First, all euphorbias exude a milky sapt or latex, which in many species is very bitter, burning, or poisonous; in others, useful as a purgauve or emetic, such as ipecac; and in still others, a source of low-grade rubber. In the Cactus family such milky sap is a rarity, occurring only among certain species of MammlUaria* Second, the euphorbias do not produce spines from cushion-like growth centers» or areoles, along the stems like cacti, but direcdy out of ihe stem itself. These spines are of three types side sh<K)ts along the stem which have aborted and become woody and sharp; stipules, or small leaflike appendages, at the base of a leaf slalk which have hardened, forming pairs of spines; or
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