地球上最原始的植物是地衣,它虽不起眼,却能在其他植物所不能生长的岩石、峭壁及冻土上生长,并成为其他植物生长的拓荒先锋。地衣共有400多种。它们长得很慢,经过10年艰苦生长的地衣,往往还小得令人难以察觉。因此,当你看到一片直径十几厘米的地衣时,应该想到,它已经在那里生存了几百年了。地衣虽然生长速度缓慢,但在千百万年的时间当中,却有足够的时间蔓延开去。它们不仅能分泌出一些特殊的化学物质将岩石表面分解成微小的砂粒,进而形成土壤,而且它们的遗体腐烂分解 The most primitive plant on Earth is lichen, which, although modest, grows on rocks, cliffs and permafrost that other plants can not grow and is a pioneer in the growth of other plants. Lichens a total of more than 400 kinds. They grow slowly, and after ten years of hard-growing lichens, they are often too small to detect. So when you see a lichen that is ten centimeters in diameter, you should remember that it has lived there for centuries. Although lichens grow slowly, millions of years have enough time to spread. They can not only secrete some special chemicals to decompose the rock surface into tiny sand, and then form the soil, and their decay and decomposition of the body