QUESTIONS AND ANSWERS 37 



QUESTIONS AND ANSWERS 



[Editorial Note. Teachers and others are again urged to send to The 

 Review questions which interest them. Now that the magazine is a monthly 

 we hope to give answers without great delay.] 



Sleep Of Plants. In answer to the question " Is it known why plants 

 go to sleep," interesting information will be found in chapter 6 of Darwin's 

 " Movements of Plants." Miall, in his " House, Garden, and Field," page 

 124, answers the question as follows : 



" Of what advantage is the trefoil leaf to the clover ? Watch the leaves 

 at sundown, and you will see that they fold up when there is no more sun- 

 light to be absorbed, and when radiation of heat to the cold sky is to be 

 feared. The division of the leaf into distinct leaflets facilitates the operation 

 of folding ; two of the leaflets droop until they become vertical, one edge 

 being turned towards the ground, and the other towards the sky ; then the 

 third leaflet folds over the other two, and forms a ridged roof above them. 

 Instead of broad surfaces, onlv a single edge, answering to the midrib of the 

 centra] leaflet, is turned towards the sky, and the radiation of heat is checked 

 in proportion as the radiating surface is diminished. 



The Darwins ascertained by experiment the effect of preventing leaves 

 from going to sleep on a clear, cold night. The leaves of a variety of plants 

 were pinned open on sheets of cork, or otherwise forced to remain in the 

 horizontal position. Many were hurt, and some killed, while others, whose 

 movements were not impeded, either escaped, or at least suffered much less. 

 Clover and wood-sorrel leaves, when pinned open, condensed large drops ot 

 dew, a proof that they had become chilled, while those whiih were uncon- 

 strained remained perfectly dry. 



How are the drooping and erection of the leaflets of clover effected ? 

 If we look carefullv at the meeting-place of the three leaflets, we shall see a 

 kind of cushion, and just beyond it three short cylindrical stalks. Part of 

 each cylindrical stalk is different in texture from the rest ; it is glossy, semi- 

 transparent, and transversely wrinkled. "" Here is the organ of movement for 

 the leaflet." 



American Nature-Study Society. In answer to several inquiries, we 

 have failed to find any reference to any regularly organized national society of 

 representative nature-study workers. It seems probable that the inquirers 

 have seen references to an advertising scheme of a well known publishing 

 house which is selling sets of books to local " clubs " arranged by agents of 

 the publishing company. 



References On Buds. In answer to a request for suggestions for studv 



