I have recently returned from an extended stay in the Succulent Karoo. one of the unique biomes of South Africa. To many people this arid region appears boring and of little ecological value however nothing could be further from the truth. This area has the greatest plant diversity of any arid area in the world and is home to a staggering 3,000 different succulent species. Many of these bear showy flowers when conditions are suitable and most (like that shown below) are members of the Mesembryanthemaceae (sometimes classified as Aizoacaea).
As you can see, the leaves of these plants are succulent and serve to store water when it is available. They are also cylindrically shaped in order to reduce the ratio of surface area to volume and therefore the rate of water loss. The remarkable seed capsules of these plants are described as being hydrochastic, which means that they only open when wet. This is an adaptation to ensure that the seeds are only released when there is sufficient water for germination. Furthermore they are designed in such a manner that the seeds are expelled from the capsule by the force of a raindrop, ensuring that they only released when the rainfall is substantial.