1891 •] The sling 'fruit of Cryptotenia. 301 



where it was held to where it lay was nearly five feet, and, 

 being quite close to the nearer edge of the table, it must have 

 remained about where it dropped. The line of direction taken 

 varied but slightly from that along which the blow was deliv- 

 ered. By spreading papers on the floor and experimenting 

 when standing I have found the carpels lying eight feet back 

 of the vertical in which the stem was held. This is a longer 



1 • 



distance than would ordinarily be reached by fruit thrown 

 from a plant at its common height. 



Thescatteringof the fruit along the shorter radii of the ellip- 

 tical area may be explained by the form of branching and in- 

 florescence of the plant. There are several branches termin- 

 ating in compound umbels, and the ultimate divisions of the 

 stem in the rays of the umbellets are sufficiently numerous to 

 point in all directions. By the principle of physics known as 

 the composition and resolution of forces, resultants will be ob- 

 tained from the application of a single force and the position 

 of the carpels and their adhesion to the carpophore to coin- 

 cide with numerous radii. But the distance to which a carpel 

 may be thrown along these lines will necessarily be less than 

 that coinciding with the longer diameter, for the length of a 

 resultant is less than the sum of its components when forces 

 act at an angle with each other, and their intensity is dimin- 

 ished. This, in connection with features previously an- 

 nounced, accounts for the shape of the area covered by the 

 fruit. 



Longitudinal sections of the branches of Cryptotaenia show 

 that it is well supplied with dotted and spiral ducts, the spiral 

 being abundant. They are very long and numerous near the 

 pith, and will contribute to the elasticity of the stem. 



The only other way of accounting for the behavior of this 

 plant in scattering its fruit appears to be that it acts like a 

 bat and ball, the rays of the umbellets striking the carpels 

 and knocking them off, either by their forward movement or 

 on their return. But they seem too slender to have this effect 

 on the relatively heavy fruit, the missile being considerably 

 larger than the body striking it, and suspended in such a way 

 as to receive the blow at the lower end alone. Still this may 

 enter into the process and help in some cases. The mechan- 

 ism of a missile attached to the end of a spring, or even 

 rigid body, in such a manner as to be easily thrown off by its 

 motion explains the action much more effectually. Here the 



