606 



Sir John LnhhocJc 



[Feb. 18, 



more or less inclined to its axis (Fig. 9). Consequently, when the pod 

 bursts it does not, as in the case of Cardamine, roll uj) like a watch- 

 spring, but twists itself more or less like a corkscrew. 



I have mentioned these species because they are some of our com- 

 monest wild flowers, so that during the summer and autumn we may, 

 in almost any walk, observe for ourselves this innocent artillery. 

 There are, however, many other more or less similar cases. Thus the 

 Squirting Cucumber {Momordica elaterium), a common plant in the 

 south of Europe, and one grown in some places for medicinal purposes, 

 effects the same object by a totally different mechanism. The fruit is 

 a small cucumber (Fig. 10), and when ripe it becomes so gorged with 

 fluid that it is in a state of great tension. In this condition a very 



Fig. 9. 



Fig. 10. 



Vicia Scpium. 

 The lino a b shows the direction of the woody fibres. 



The Squirting Cucumber 

 (^Momordica elate Hum). 



slight touch is suflicient to detach it from the stalk, when the pressure 

 of the walls ejects the contents, throwing the seed some distance. In 

 this case of course the contents are ejected at the end by which the 

 cucumber is attached to the stalk. If any one touches one of these 

 ripe fruits, they are often thrown with such force as to strike him in 

 the face. In this the action is said to be due to endosmosis. 



In Ct/danthera, a plant allied to the cucumber, the fruit is unsym- 

 metrical, one side being round and hairy, the other nearly flat and 

 smooth. The true apex of the fruit, which bears the remains of the 

 flower, is also somewhat eccentric, and, when the seeds are ripe, if it 

 is touched even lightly, the fruit explodes and the seeds are thrown to 

 some distance. The mechanism by which this is effected has been 



