88 PHYSIOLOGICAL SEKIES. 



C. 4. Portion of stem and leaves of Hedysarum gyrans. The 

 main leaves assume the normal diurnal and nocturnal 

 positions. The small lateral leaflets are in constant 

 spontaneous periodic movement occupying a few minutes, 

 the temperature must be high (at least 22 C.). 



C. 5. Two portions of stem with leaves attached of a Scarlet- 

 runner (Phaseolus multifiorus). A swollen region at the 

 bases of the main leaf-stalks and leaflets constitutes a special 

 motile organ. In the absence of light the upper halves 

 of the motile organs of the leaflets become more turgid, 

 causing the leaflets to droop ; at the same time the motile 

 organ of the main leaf-stalk becomes more turgid below, 

 thus raising the leaf-stalk into a more vertical position. 



C. 6. A branch of Mimosa pudica, with two leaves ; one of them 

 is in the expanded state ; the other contracted, but erect. 

 0. C. 29. 



" Although one only of the pinnules be touched, the contractile 

 movement is quickly propagated along the other three: it consists 

 of an approximation of the upper surfaces of the opposite subleaflets 

 to each other, with an overlapping of those of the same side." 

 John Hunter, MS. Croonian Lectures, No. 1. 



Hunterian. 



C. 7. Two portions of stem with leaves attached of a Sensitive 

 Plant (Mimosa pudica). The diurnal and nocturnal 

 positions are shown. The nocturnal position is rapidly 

 assumed on the slightest irritation. It probably is of use 

 in protecting the leaves from injury by tropical rain-storms. 

 Special motile organs are well denned. 



ANIMALS. 



INVERTEBRATA. 



C. 8. Part of the margin of a large Medusa (Rhizostoma ccerulea), 

 on the inferior edge of which the membrane is disposed in 

 numerous minute plicse, running in the direction of the 

 circumference, and giving to it a fibrous or muscular 

 appearance. 



