世界文化之非洲动植物（37）——金合欢

鹰击长空

　　我走遍世界，却唯独没有去过非洲。然而，当你初步了解了非洲之后才知道，非洲不是你想象中的荒蛮之地，非洲也有美丽的风景、可爱的动物和艳丽的花朵，通过阅读这些英语短文，可以细细的品味非洲的美丽。

　　Umbrella Thorn Acacia is one of the most recognizable trees of the African savanna . It grows in sand dunes and rocky grounds of Africa ' s grasslands . Acacias grow in areas with annual rainfall as low as 4 cm . This tree can survive in 122° F temperatures during the day , and freezing temperatures at nights .

　　The savanna that the Acacias live in is hot and dry in the respective summer of the Southern Hemisphere . During the winter months the savanna gets a lot of rain .

　　The Umbrella Thorn Acacia grows up to 20 meters high and has a spreading , flat - topped crown that gives it its name . The bark on the Acacia is black to gray in color and feels rough . The branches on the Acacia are gnarled .

　　It has two types of thorns on the branches ; long , straight , brownish thorns and shorter , hooked thorns that grow alongside each other . The thorns grow in pairs and disguise themselves in the clusters of flowers that grow on the Acacia . The flower clusters have up to 400 white , puffball flowers that grow on a twig on the Acacia .

　　The Acacia ' s leaves are composed of small alternate leaflets on a central rib . The Acacia ' s leaves are 2.5 cm long and 1 mm wide . The seeds are 8 to 12cm long twisted pods . The Acacia ' s belong to the family " Mimosaceae ", and until recently was known as the " Mimosa Tree ".

　　One of the Acacia ' s adaptations to hot and dry conditions is a deep taproot , which can reach 115 ft under the ground . This adaptation helps it get the water during the dry spells . A second set of roots spread out Just under the ground about twice the area of the crown .

　　The little leaves of it prevent water loss . The Acacia ' s umbrella - shaped tops enable the tree to capture large amounts of sunlight with the smallest possible leaves . The thorns are used to keep the savanna animals away from eating the leaves , flowers , and seedpods . The only animal that is immune to the thorns is the giraffe .

　　The Acacia provides shade for the animals of the savanna . The trunk of the tree makes very good charcoal and firewood . The flowers on the Acacia provide a good source of honey in some regions . The stem of the tree is used to treat asthma , and diarrhea . The bark of the Acacia is used as a disinfectant , and the pods are used to make porridge .

　　The Acacia is not endangered , and it is actually plentiful . There are over 700 species of the Acacia in Africa .

　　伞状的金合欢是非洲稀树草原上最知名的树种之一。它生长在非洲草原的沙丘和岩石地带。这种树生长在年降雨量只有4厘米的地区。白天能在华氏122度的温度下生存，晚上能在冰点下生存。

　　在南半球的夏季，它生活的热带稀树草原炎热干燥。在冬季的几个月里，热带稀树草原雨水充沛。

　　金合欢可长到20米高，其顶部平展，树冠因此得名。金合欢上的树皮颜色从黑色到灰色，摸起来粗糙。树上的树枝多节。它的树枝上有两种刺：一种是长而直的褐色刺，另一种是短而钩状的，它们并排生长。

　　荆棘成双成对地长在金合欢树上的花丛中伪装自己。这些花簇长在金合欢树的树枝上，长着多达400朵白色的马勃状花朵。

　　金合欢的叶子是由位于中央肋骨上的小叶交替组成的。相思树的叶子长2.5厘米1 mm宽。种子是8到12厘米长的扭曲的豆荚。它属于含羞草科，直到最近才被称为含羞草树。

　　金合欢对炎热干燥环境的适应能力之一是它深长的主根，它可以长到地下115英尺。这种适应性帮助它在干旱期获得水分。第二组根在地下展开大约是树冠面积的两倍。

　　它的小叶子可以防止水分流失。它伞状的树顶使其能够以最小的叶子吸收大量的阳光。荆棘是用来阻止草原动物吃树叶、花朵和种荚。唯一对刺免疫的动物是长颈鹿。

　　金合欢为热带草原上的动物提供了荫凉。树干可以制成很好的木炭和木柴。花朵在某些地区提供了很好的蜂蜜来源。这种树的茎被用来治疗哮喘和腹泻。树皮被用作消毒剂，豆荚被用来煮粥。

　　金合欢树并没有濒临灭绝，而且数量非常丰富。非洲有700多种金合欢属植物。