VI] FIXITY OF POSITION IN PLANTS 99 



example, the double Coco-nut of the Seychelles 

 {Lodoicea) may be cited, probably the largest single- 

 seeded fruit in the Vegetable Kingdom. Again, 

 in some cases animal agency is used, externally by 

 hooks and barbs on the surface of the seed or fruit, 

 which catch upon the coat of a passing animal: or 

 internally by pulpy developments, which attract the 

 animal as food, and the seeds swallowed with the 

 pulp are deposited with the excreta at a distance. Or 

 plants may develope mechanically effective means of 

 propulsion of their own. The common Broom and 

 the hairy Bitter Cress have explosive fruits, which 

 scatter the seeds far and wide. An extreme case is 

 that of the Euphorbiaceous Sand-Box tree (Hura 

 crejntans), the woody fruit of which explodes with a 

 report like a pistol shot, and scatters the relatively 

 large seeds to a considerable distance. Or the 

 principle employed may be that of the common 

 squirt, as in Echalllum, the Squirting Cucumber, 

 which extrudes its semifluid pulp, seeds and all, to a 

 distance of many feet, as it detaches itself from its 

 stalk when ripe. These are merely examples of the 

 varied artifices employed by plants for the distribu- 

 tion of tlieir germs. The raison d'etre of all of them 

 is idtimately to be found in the fixity of position, 

 Avhich the plant assumes at once on germination. 



It is thus seen that, in the first place, the encyst- 

 ment of the protoplast within a firm cell-wall, and 



7—2 



