PEA FAMILY 



on the two side leaflets will be seen to twist and ap- 

 proach each other until their upper surfaces come into 

 contact. At the same time they bend downward. 

 The terminal leaflet merely rises up without any twist- 

 ing and bends over until it rests on and forms a roof 

 over the edges of the two united lateral leaflets. When 

 this movement is complete the terminal leaflet stands 

 at night horizontally with its lower surface fully ex- 

 posed. Leaves vary somewhat, but this is the typical 

 arrangement. 



Charles Darwin, writing upon this subject, says: 

 ''The fact that the leaves of many plants place them- 

 selves at night in widely different positions from what 

 they hold during the day, but with the one point in 

 common that their upper surfaces avoid facing the 

 zenith, often with the additional fact that they come 

 into close contact with opposite leaves or leaflets, 

 clearly indicates, as it seems to me, that the object 

 gained is the protection of the upper surfaces from 

 being chilled at night by radiation. There is nothing 

 improbable in the upper surface needing protection 

 more than the lower, as they differ in structure." 



The flowers of all the Clovers are papilionaceous, 

 but, crowded as they are in heads, the petals have 

 grown together and become tubular. 



The generic name Trifolium alludes to the three- 

 parted compound leaf which is characteristic of the 

 genus. The name Clover is thought to have been de- 

 rived from the Latin clava, meaning club in connec- 

 tion with the mythical three-headed club of Hercules 

 which the Clover leaf is supposed to resemble. The 

 clubs on playing-cards are believed to have originated 

 from the Clover leaf. Among the common names of 



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