THE PROMISE OF- THE PLANT THAT IS TO BE 469 



FIG. 575. SEED OF WOOD- 

 SORREL. 



The elastic outer integument is burst- 

 in? open to expel the seed. 



It is therefore a matter for thankfulness that 

 provision has been made in nature for the dis- 

 persal of the fruits and seeds of plants. This 

 great end is effected in many ways. Sometimes 

 the plant ejects its own offspring in a more or less 

 forcible manner by means of special tissues which 

 act as slings, catapults, etc. : sometimes the fruits 

 themselves are capable of creeping or hopping 

 along the ground ; sometimes they are provided 

 with plumes, aeroplanes, or with envelopes filled 

 with air, which render them so buoyant that they 

 are able to perform long aerial journeys, the least breeze being sufficient 

 to carry them along : sometimes the wind lays hold of them when on the 

 ground and drives them forward with rapidity: sometimes the water is 

 their friend, and stream and torrent, lake and ocean, become instrumental 

 in transporting them to new and distant homes ; sometimes the fruits are 

 furnished with hooks or sticky secretions which facilitate their dispersion by 

 birds and other animals. 



The Wood-sorrel \0xalis acetosella), whose delicate white blossoms may 

 be often seen peeping among the mossy uncovered roots of forest-trees, is 

 one of our commonest wild-flowers. It offers a familiar example of plants 

 with sling fruits. When the seeds are ready for dispersion, the capsules 

 containing them burst open, and the strong tense tissue which covers each 

 of the seeds being 

 ruptured at the same 

 time, the seed is 

 jerked out to a con- 

 siderable distance 

 (figs. 574, 575). In 

 the Squirting Cu- 

 cumber (Ecballium, 

 daterium. fig. 576 1 

 the arrangement is 

 even more curious. 

 The seeds are con- 

 tained in a juicy 

 pulp, which fills the 

 fleshy and bristly 

 ' cucumber," and 

 which is kept from 

 bursting out by the 



hooked and stopper- ^ 576> _ SQUIKTING CUCUMBER (Ecballium elaterium). 



like Stalk. When when the froit is ripe it breaks off from the stalk, and from this point the seeda 

 the Seeds are ripe, and pulp are squirted out with force. 



