438 University of California Publications in Botany [Vol. 5 



The diameter of the limb (fig. 1, e) is then read off in millimeters on 

 the scale on the circular disc (pi. 54, a). The knurled head is now 

 turned still more to the right until the line n is under the end of the 

 tube (fig. 1, d). The length of the tube (fig. 1, /) is then read off. 

 The bar m (pi. 54) is next turned back to the left to get the diameter 

 of the second limb (fig. 1, g) and then moved to the right to obtain 

 the length of the second tube and so on. 



This apparatus or some modification of it would seem useful in 

 measuring a wide variety of objects. Leaves, especially, can be 

 measured on it very successfully. 



