THE MECHANICS OF NUTATION MOVEMENTS 



measurements of the distances between exactly opposite pairs of marks on the two 

 sides of the active zone of the perianth. From these hourly measurements percentage 

 values have been calculated for the opposed sides. The half of the algebraic sum of 

 the two values gives the percentage growth of the actual or ideal middle lamella 

 (Tables 3 and 4). In Tables i and 2 only this average growth is given, but since in 

 these estimations with the flower of the Crocus the concave side remained of the same 

 length or shortened very slightly, twice the average growth gives that of the convex 

 side. 



The values in Tables i and 2 1 are the averages of six separate estimations, those 

 of Table 3 2 of three, and those of Table 4 are obtained from three separate flowers 3 . 



The measurements were made on a single remaining perianth-segment of Crocus 

 and Tulipa, and on a single remaining floret of Leontodon. Table i shows that the 

 cooling of the flower of Crocus 4 produced a pronounced acceleration of growth in 

 fifteen minutes, which rapidly lessened and had almost ceased after half an hour. 

 A feeble transitory acceleration of growth also appears in Table 2, but is less evident 

 (1-51 as compared with 1-03). A pronounced transient acceleration is, however, 

 shown in Table 3, and after two hours a return curvature is shown, which is accom- 

 panied by an acceleration of growth on the outer side of the perianth, and a retardation 

 on the inner side. 



TABLE i. Crocus sp. Percentage Growth of the Middle Lamella per hour. 



TABLE 2. Crocus sp. Percentage Growth of the Middle Lamella per hour. 



TABLE 3. Tulipa Gesneriana (Due van Toll). Percentage Growth per hour. 



1 Pfeffer, Period. Bewegungen, p. 125, Tables XI b, and p. 127, Table XIII b. 



a Jost, 1. c., p. 354. 



3 Pfeffer, 1. c., p. 27, Tables VII b and VII c. 



* A large white-flowered garden variety was used. 



