Many people suffer from color blindness in some way. Women are luckier, only about one in two hundred is affected in this matter. Perhaps, after all, it is safer to be driven by a woman!

There are different forms of color blindness. In some cases a man can not see deep red. He may think that red, orange and yellow are all shades of green. Sometimes a person cannot tell the difference between blue and green. In rare cases an unlucky man may see everything in shades of green — a strange world indeed.

Color blindness in human beings is a strange thing to explain. In a single eye there are millions of very small things called “cones”. These help us to see in a bright light and to tell difference between colors. There are also millions of “rods” but these are used for seeing when it is nearly dark. They show us shape but no color.

Some insects have favorite colors. Mosquitoes (蚊子) like blue but do not like yellow. Red light will not attract insects, but a blue lamp will. In a similar way human beings also have favorite colors. Yet we are lucky. With the aid of the cones in our eyes we can see many beautiful colors by day, and with the aid of the rods we can see shapes at night. One day we may even learn more about the invisible(看不见的)colors around.

The Secret Language of Plants

Talking plants have long been a thing of myths and legends. Many cultures have stories of talking trees that give advice as well as warnings to people. Alexander the Great and Marco Polo were said to have visited such a tree in India. And in some modern stories, such as the film Avatar, trees can communicate with animals and people.

With us long believing that talking plants are fantasy, new research has revealed something amazing：it appears that plants can communicate after all.

It has been known for some time that plants use chemicals to communicate with each other. This happens when a plant, say a bean plant, gets attacked by insects. The plant releases tiny amounts of chemicals from the leaves that are being eaten. This is like a warning, or a call for help: “I’m being attacked!” When another bean plant detects the chemicals from its injured neighbour, it starts to release its own, different chemicals. Some of these chemicals drive insects away. Others attract insects—the wasps! The wasps kill the insects that are eating the bean plants. Scientists hope to learn more about this plant warning system, so that we can use it to grow crops without pesticides.

More surprisingly, plants also use sound to communicate. People can’t hear these sounds, but plants are making them. Some plants make noises with their roots. Corn and chilli plants do this. They also “listen” to the noises from other plants. A chilli plant can tell if a neighbouring plant is helpful, or unfriendly. Some trees make clicking noises when there is not enough water, indicating drought is arriving.

Most surprisingly of all, plants have an amazing system of communication that can link nearly every plant in a forest. Scientists call this system the “wood wide web”．It is in some ways similar to the Internet we use.^]While the Internet is a worldwide network of computers linked by cables and satellites, the wood wide web is linked underground by fungi. This fungal network links the roots of different plants to each other. Using the wood wide web, plants can share information and even food with each other. For example, some pine trees can send food to smaller pine trees to help them grow. But just like our own Internet, the wood wide web has its own version of “cybercrime”．Plants can steal food from each other, or spread poisons to attack other plants. Perhaps one day scientists will learn how to create a “firewall” to help prevent these attacks within the wood wide web.

Scientists are learning more every day about the secret ways in which plants talk to each other. Who knows? Maybe one day we will know enough about plant communication to be able to “talk” with them ourselves.

To discover whether bees can see colors, the following experiment is set up. A table is put in a garden and on the table is a piece of blue cardboard (硬纸板) with a drop of syrup (糖浆) on it. After a short time, bees come to the syrup. The bees then fly to their hive (蜂窝) and give the syrup to other bees in the hive. Then they return to the feeding-place which they have discovered. After a while, the blue cardboard with the syrup on it is taken away. Instead of this card, a blue card is now put on the left side of the first feeding-place and a red card to its right. These new card have no syrup on them. Thus, the blue card is on the left, the red card on the right, and there is nothing where the first blue feeding-card used to be. Very soon bees arrive again, and fly straight to the blue card. None to the red card.

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