Calcium chloride and table salt are not the only substances 

 deposited here. Also present are Glauber's salt, a hydrate of 

 sodium sulphide; gypsum, or calcium sulphate; Epsom salts, or 

 magnesium sulphate heptahydrate; magnesium chloride; potas- 

 sium chloride; and others. There are estimated to be over seven 

 billion tons of salt in this basin. When fresh water does find its 

 way here from the mountains and the infrequent rains, it floats 

 on top of the salt water and only slowly mixes with it, and in 

 winter miniature icebergs may form on the surface and ride 

 about. In some of the dry basins there are incredible beaches and 

 accretions of salts and alkalis that look just like snow and ice. 



It is curious that the name "salt bushes" has been given to 

 plants that happen to be tolerant of high concentrations of 

 alkalis, not of salts. It is a fact that plants— which can readily 

 manufacture acids— can cope with alkalinity by neutralizing it 

 but are unable to cope with the more stable salts. Thus there is 

 a dearth of vegetation around salt pans but often a quite profuse 

 growth around alkaline deposits, notably any that still contain 



ELECTRIC PLANTS 



Much of the Great Basin, where it is not entirely bare due to 

 these chemical deposits or marching sand dunes, is covered with 

 a rash of stunted plants, growing well separated as if planted 

 deliberately. This continues to the tops of most of the mountains 

 and looks at first quite homogeneous. Closer examination, 

 however, shows an astonishing variety of different plants, all 

 growing in much the same way and looking surprisingly alike. 

 All of them have minute leaves or none at all. Almost all bear 

 thorns or prickles or veritable spikes, often all over and in great 

 density. Such structures are prevalent in the floras of deserts and 

 other arid regions in warmer latitudes, but not in circumpolar 

 regions. Prickles or spikes on plants present an interesting puzzle. 



While temperate regions have their share of thorny plants 

 and equatorial areas are rife with spiky things, neither can 

 display anything to compare with the prickles and spikes of the 

 arid regions. In our deserts and drier scrub zones we find all 

 manner of spiky plants apart from the cactuses, such as the 

 mesquite, the huisache, the cat's-paw, the bull thorn, and 

 countless others. The purpose of these spines has long been 

 debated. It is manifest that thorns and especially hooks on seeds 

 or bits of plants that may proliferate are valuable, in that they 

 may become attached to animals and so disseminated. Also, the 

 spiny cover of a barrel cactus has been shown to cut down the 

 amount of heat striking the skin of that plant by as much as 

 20 per cent. Further, although spikes and spines may deter some 

 animals from eating such plants as bear them, most larger ani- 

 mals of dry areas, even the worthy cow, seem to be able to chew 

 such indelicacies happily all day long. But none of these reasons 

 explains the profusion of such devices. Some more adequate 

 explanation is needed, and one most interesting suggestion has 

 been made. 



Plants with leaves breathe through the tiny pores called 

 stomata on the undersurfaces of their leaves. These can open 

 and shut to regulate evaporation of water vapor from within. 

 Constant evaporation at the tops of trees causes a drop of 

 pressure within the plant so that sap rises. This process, called 



Utah's gulls are famous for their role in the founding of 

 the Mormon settlement in this arid region and are now 

 in the Utah state seal. 



240 



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