PLANT SCRIPTS 7 



shortening might be accomplished by attaching the thread 

 nearer to the fulcrum. Proceeding in the manner indicated, 

 any magnification, however high, can be obtained. 



Reduction, again, may be effected with equal ease. 

 When the point of attachment is exactly midway between 

 the pulvinus and the tip of the leaf, then the movement 

 executed by it will be half that described by the extremity 

 of the leaf. By bringing the point of attachment nearer 



Fig. 2. — Response-curve of primary leaf of Mimosa ; the vertical 

 lines below the record indicate intervals of one minute each. 



to the pulvinus, we can obtain whatever reduction may be 

 required. 



The resultant magnification or reduction of the record 

 will thus depend, in any given case, on two factors — namely, 

 the relation between the length of the writer and the length 

 of the lever-arm, on the one hand ; and, on the other, the 

 relation between the distance of the point of attachment 

 from the pulvinus and the entire length of the leaf. 



Thus if the lever produce a magnification of four, and the 

 point of attachment cause a reduction to half, the resulting 

 magnification will be 4 X | = 2. As the movement of the 

 primary petiole of Mimosa is considerable, the records taken 

 are normally either equal or reduced to two-thirds. A 

 record taken in this manner is given in fig. 2. The height 



