>65 The Early Settlers in North America
      The North American frontier changed some of the characteristics of the pioneers of the 1750's and intensified others. They were, as a group, semiliterate, proud,and stubborn, as dogged in their insistence on their own way of life as pine roots cracking granite to grow. Perhaps their greatest resource was their capacity to endure. They outlasted recurrent plagues of smallpox and malaria and a steady progression of natural accidents. They were incredibly prolific. Squire Boone's family of eight children was small by frontier standards. James Roberson, an eventual neighbor of Boone's and the founder of Nashville, had eleven children. Twice married John Sevier, the first governor of Tennessee, fathered eighteen; his longtime enemy, John Tipton, also twice married, produced seventeen. The entire assets of one of these huge families often amounted, in the beginning, to little more than an axe, a hunting knife, an auger, a rifle, a horse or two, some cattle and a few pigs, a sack of corn seed and another of salt, perhaps a crosscut saw, and a loom. Those who moved first into a new region lived for months at a time on wild meat, Indian maize, and native fruits in season. Yet if they were poor at the beginning, they confidently expected that soon they would be rich. In a way almost impossible to define to urban dwellers, a slice of ground suitable for farming represented not just dollars and cents, but dignity. The obsession brought shiploads of yearners every week to Boston, New York, Philadelphia, Baltimore, Charles Towne, and Savannah. It sent them streaming westward into the wilderness after their predecessors to raise still more children who wanted still more land.

      北美早期殖民者
      北美的边远地区改变了18 世纪 50 年代拓荒者的一些特点，而强化了他们的另一些特点。 作为一个整体，他们是半文盲，高傲并且顽固。 他们坚持自己的生活方 式就象松树根在花岗石中爆缝生长。 也许，他们最大的资源是忍耐能力。 他们熬过了经常 性的天花、疟疾等瘟疫及一系列自然灾难。 他们出奇地多育。 依他们的标准，斯夸尔布恩 有八个孩子是少的了。 最后成了布恩的邻居并且是那士维的建造者的詹姆士·罗伯逊有 11 个孩子。 曾结过两次婚的约翰·塞维尔--田纳西州的第一位州长，生了 18 个孩子，他长期 的仇敌，约翰·提普敦也结过两次婚并有 17 个孩子。 最初，在这些庞大的家庭中，全部的 财产合起来也不过是一把斧头、一把猎刀和一根钻子，一条步枪，一两匹马，牛和猪，一袋 玉米种子和一袋盐，或可能还有一把锯子和一台织布机。 那些新到一个地区的人们一连数 月靠野味、印第安玉米和季节性野果维持生活。 然而，即使最初很贫穷，他们自信很快就 会富起来。 一块适合耕种的土地不仅仅代表着金钱，更意味着尊严。 这一点是无法向城市 居民解释的。 这一固执的想法每周都将整船整船的渴望者带往波士顿、纽约、费城、巴尔 的摩、查尔斯城和萨瓦那。 跟随着他们的先行者，这些渴望的人们象潮水一般涌向荒野， 去生养更多的子女，而这些子女又将需求更多的土地。
>66 Plants in the Deserts
      Some cacti, like the saguaro, grow to tree size, but true trees need more moisture than most desert environments can supply, so they are scarce on deserts. Close to streambeds, cottonwoods can sometimes be found. Though these streams are dry most of the year, water flows there longest and is usually available fairly close to the surface. Elsewhere, trees must send taproots deep into the hard baked desert soil to draw on underground water. Perhaps the most widespread family of trees on the world's deserts is the acacia, whose taproots drill down as far as 25 feet(7. 5 meters). The mesquite common on North American deserts in both tree and shrub forms, does not begin to grow above ground until its root system is completely developed, ensuring the plant a supply of moisture. The roots of shrubs and trees help to hold the desert soil in place. Their stalks and branches also act as screens to keep the wind from sweeping great drifts of sand along the surface. These services are vital if a desert is to support life. Scientists estimate that a desert needs year round plant cover over 20 to 40 percent of its surface. If shrubs are too far apart - separated by a distance greater than five times their height - soil around them is likely to blow away. Without the shelter of established shrubs, new seedlings will have difficulty in getting a start. On the other hand, plants that are too close together may compete for underground moisture. To protect themselves from this competition some shrubs give off a substance that kills young plants that sprout too close to them. In addition to a few varieties of trees and tough shrubs, most deserts have grasses, herbs, and other annual plants. These do not compete for moisture with the longer lived growth. They spring up quickly after rains, when the surface is moist. Then, for a brief time, the desert can be literally carpeted with color. Almost as quickly as they appeared, these small plants die away. But they have developed special ways of ensuring the life of another generation when rains come again.

      沙漠中的植物
      一些仙人掌，如撒瓜罗，能长到象树那么高。 但真正的树却需要比大多 数沙漠所能提供的更多的水份，所以树在沙漠里是鲜见的。在小溪河床附近，有时能发现三 角叶杨。 尽管一年的大多数时间里这些小溪都是干涸的，那里却是水流得时间最长的地方 而且水份相当靠近地表。 其它地方树木的主根必须深入受炙烤而坚硬的沙漠底部的土壤以 吸取地下水。 在沙漠里分布最广的树或许是刺魏，其主根能深达 25 英尺(合 7 5 米)。 牧豆树属植物不论是乔木和灌木，在北美沙漠中常常可见，在它根部系统完全生长发达到能保 证提供充足的水分时才长出地面。 灌木和树的根有助于固定沙漠中的土壤，它们的茎和树 枝同时起屏障的作用，防止风从沙漠表面吹起大堆的沙。 如果沙漠要支持生命，这种作用 必不可少。 科学家估计一年之中植物必须覆盖沙漠表面的 20%到 40%。 如果灌木间隔太 远--大于它们高度的 5 倍--周围的土壤就可能被吹走。 如果没有这些灌木作为保护，新的种 子很难生长。 另一方面，植物相互靠得太近却会引起竞争地下水分。 为避免竞争，一些灌 木会释放一种物质来杀死那些距他们太近发芽的植物。 除了一些种类的树木和顽强的灌木 外，大多数沙漠里还有青草、草本植物和其它年生植物。 它们并不与长期生长的树木竞争 水份。当雨后地表还潮湿时它们就迅速发芽，然后在一个短时间里，给沙漠铺上绿色地毯。 这些小植物很快就消失了，几乎就象它们长出来时那样迅速，但它们已发展了特殊方式来保 证在下次降雨来时下一代的生命。