120 



PLANT RELATIONS. 



suddenly curls up and throws the seeds (see Fig. 123). The 

 squirting cucumber is so named because it becomes very 

 much distended with water, which is finally forcibly ejected 

 along with the mass of seed. An " artillery plant " common 



in cultivation discharges its 

 seeds with considerable vio- 

 lence ; while the detonations 

 resulting from the explosions 

 of the seed-vessels of Hiira 

 crepitans, the " monkey's din- 

 ner bell," are often remarked 

 by travelers in tropical 

 forests. 



81. Dispersal of seeds by animals. — Only a few illustra- 

 tions can be given of this very large subject. ^Vater birds 

 are great carriers of seeds which are contained in the mud 

 clinging to their feet and legs. This mud from the borders 

 of ponds is usually completely filled with seeds and spores 

 of various plants. One has no conception of the number 

 until they are actually com- 

 puted. The following ex- 

 tract from Darwin's Origin 

 of Species illustrates this 

 point : 



Fig. 126. The fruit of carrot, showing 

 the grappling appendages. — After 

 Beal. 





S^ 



Fig. 127. The fruit of coclvlebur, showing 

 the grappling appendages. — After Beal. 



"I took, in February, three 

 tablespoonfuls of mud from three 

 different points beneath water, 

 on the edge of a little pond. This mud when dried weighed only 6f 

 ounces ; I kept it covered up in my study for six months, pulling up 

 and counting each plant as it grew ; the plants were of many kinds, 

 and were altogether 537 in number ; and yet the viscid mud was all 

 contained in a breakfast cup ! " 



Water birds are generally high and strong fliers, and the 

 seeds and spores may thus be transported to the margins of 

 distant ponds or lakes, and so very widely dispersed. 



In many cases seeds or fruits develo]) grappling append- 



