We have known for a long time that flowers of different plants open and close at different times of day. This is so 1 神秘的) way of knowing the 7 . Their sense of time does not 8 information from the outside world; it is, so to speak, inside them, a kind of “inner clock”. that there seems to be no need to ask the reason for it. Yet no one 2 understands why flowers open and close like this at particular times. The process is not as 3 as we might think, as recent experiments have shown. In one study, flowers were kept in constant 4 . We might expect that the flowers, without any information about the time of day, did not open as they 5 do. As a matter of fact, they 6 to open at their usual time. This suggests that they have some mysterious(
