Jewelweeds are pretty flowers that grow in wet, shady spots all over the Northern Hemisphere. According to a recent experiment, they seem to know their own flower family —or at least, recognize whether or not they came from the same mother plant. Together with other through their leaves, but through their roots.
Scientists planted jewelweeds in pots with either siblings（兄弟姐妹）or strangers. Sibling plants were grown from seeds that came from the same mother plant. Stranger plants were grown from seeds from different plants.
When jewelweeds were planted in pots with strangers, the plants started to grow more leaves than if they had been planted alone. This response suggests that plants are competing with strangers for sunlight, since a plant with more leaves can receive more light and make more food.
When jewelweed seedlings were planted with siblings, they few a few more branches than they normally would if they were alone—but they did not start growing lots of extra leaves. This behavior suggests the plants are more likely to share resources, rather than compete.
The plants only responded this way when they shared soil. If stranger seedlings were planted in different pots and placed next to each other, for example, they did not grow more leaves. This different shows that the plants must use their roots to detect sibling plants in the same soil. In 2007, Dudley and her team studied the Great Lakes sea rocket, a plant that grows on the beach—where it may be hard to get fresh water. In that experiment, the botanists observed that when sea rockets were planed with siblings, they tolerated each other. But when they were planted with strangers, the sea prickets reacted by working extra hard to grow lots of roots, but not extra leaves.
The different types of plants may react in different ways, but they have one thing in common: the roots. In both experiments, on Jewelweeds and sea rockets, the key was the shared soil—and other plant species may turn out to show similar behavior. These experiments, as well as earlier experiments, suggest “The phenomenon is quite common.” Says Hans de Kroonof, an ecologist in the Netherlands.
57．In Paragraph 1, the author mentions a recent experiment of Jewelweeds to___________.
A．make a comparison  B．introduce a topic
C．describe a pretty flower   D．put forward a new theory
58．What can we know from the experiments done by scientists?
A．Jewelweeds can grow in the Northern Hemisphere.
B．Jewelweeds can grow in wet, shady spots.
C．Jewelweeds are more friendly to their siblings than to stranger plants.
D．jewelweeds can recognize their siblings through leaves.
59．If jewelweeds and their siblings are planted in different pots and placed close to one another, they will___________.
A．start to grow more leaves       B．detect the strangers 
C．compete with sibling plants     D．grow normally
60．The best title of the passage would be___________.
A．Flower family knows its roots
B．The growing conditions of Jewelweeds
C．Jewelweeds and sea rockets
D．The stranger plant recognize each other