i66 



THE POPULAR SCIENCE MONTHLY. 



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 pur- 

 poses, effects the same object by a -totally different mechanism. The 





Fig. 9. Vicia sepium. The line a b shows 

 the direction of the woody fibres. 



Fig. 10. The Squirting Cucumber {Moniordica 

 elaterium.) 



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 slight touch is sufficient to detach it from the stalk, w^hen the 

 pressure of the walls ejects the contents, throwing the seed some dis- 

 tance. 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 Cyclanthera, a plant allied to the cucumber, the fruit is un- 

 syrametrical, 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 

 described by Ilildebrand. The interior of the fruit is occupied by 

 loose cellular structure. The central column, or placenta, to which 

 the seeds are attached, lies loosely in this tissue. Through the solution 

 of its earlier attachments, when the fruit is ripe, the column adheres 

 only at the apical end, under the withered remains of the flower, and 

 at the swollen side. When the fruit bursts, the placenta unrolls, and 



