356 FRUITS AND SEEDS 



nent, by the ocean currents. Darwin estimated that about 

 one kind of seed in ten is able to retain its vitality in sea 

 water as long as a month. This, at the usual rate of move- 

 ment of ocean currents, might mean a successful journey 

 of over a thousand miles. 



There are many floating fruits, however, which soon 

 decay in water, especially in salt water. The coconut, 

 often seen floating in tropical seas, loses its vitality in the 

 water in a few days. There are some plants of the tropical 

 beaches, however, whose seeds have been found to be un- 

 injured after floating in rough, salt water for 143 days. 



C. Animals. — The distribution of seeds and fruits by 



animals may be said 

 to be of two kinds, 

 voluntary and involun- 

 tary. Of the fruits dis- 

 tributed involuntarily, 

 those with hooked ap- 

 B pendages are most 



Fig. 159. — The fruits of cocklebur (.4) and , . 



burdock (B) showing the hooked appendages familiar. (bee Figure 



by which they become attached to the coats J?Q.) Besides burdock 

 of passing animals. — After Kemer. ■, 1 1 i 



and cocklebur, many 

 other common weeds use this method of distribution. 



Of the edible fruits, some, on account of their edibility, 

 are of much service in placing seeds favorably for germi- 

 nation, while for others edibility appears to be a loss rather 

 than a gain. It all depends upon whether the seeds as 

 well as the pulp of the fruit are digested. 



The seeds which pass from the body of animals uninjured 

 are quite likely to be deposited in conditions favorable to 

 the germination and later growth of the young plant. 



