This Lower Delta, the marisma proper, while it varies here and there by a few inches in elevation, is practically a uniform dead-level of alluvial mud, only broken by _vetas_, or low grass-grown ridges seldom rising more than a foot or two above the flat, and which vary in extent from a few yards to hundreds of acres. The precise geological cause of these _vetas_ we know not; but the calcareous matter of which they are composed--the debris of myriad disintegrated sea-shells, mostly bivalves--proves that the ocean at an earlier period held sway, till gradually driven backwards by the torrents of alluvial matter carried down by the river, and finally forced behind the vast sand-barrier now known as the Coto Doñana--the buffer called into being whilst age-long struggles raged between these two opposing forces. The fact is further evidenced by the salt crust which yearly forms on the surface of the lower marisma when the summer sun has evaporated its waters. In summer the marisma is practically a sun-scorched mud-flat; in winter a shallow inland sea, with the _vetas_ standing out like islands. There are, as already stated, slight local variations in elevation. Naturally the lower-lying areas are the first to retain moisture so soon as the long torrid summer has passed away and autumn rains begin. Speedily these become shallow lagoons, termed _lucios_--similar, we imagine, to the _jheels_ of India--and a welcome haven they afford to the advance-guard of immigrant wildfowl from the north. Plant-life in the marismas is regulated by the relative saltness of the soil. In the deeper _lucios_ no vegetation can subsist; but where the level rises, though but a few inches, and the ground is less saline, the hardy samphire (in Spanish, _armajo_) appears, covering with its small isolated bushes vast stretches of the lower marisma. The _armajo_, which is formed of a congeries of fleshy twigs, leafless, and jointed more like the marine _algae_ than a land-plant, belongs to three species as follows:-- (2) _Arthraenimum fruticosum_} } in Spanish, _Armajo_. (3) _Suaeda fruticosa_ } All three belong to the natural order _Chenopodiaceae_ (or "Goose-foot" family). The _armajo_ is the typical plant of the marisma, flourishing even where there is a considerable percentage of salt in the soil. This aquatic shrub increases most in dry seasons, a series of wet winters having a disastrous effect on its growth. The _Sapina_, above mentioned, has a curious effect when eaten by mares (which is often the case when other food is scarce) of inducing a form of intoxication from which many die. Indeed, the deaths from _Ensapinadas_ represent a serious loss to horse-breeders whose mares are sent to graze in the marismas. Cattle are not affected. [Illustration: SAMPHIRE]