FRUITS AND SEEDS AND THEIR USES 293 



those on the seeds of milkweeds (Fig. 171). The hairs 

 attached to the seed coat of the cotton are used in making 

 cotton thread and cotton cloth, and it is the presence of these 

 hairs that makes the cotton plant so valuable. Some seeds, 

 as well as fruits, are distributed by currents of water. Many 

 others lodge in the fur or on the bodies of animals. By means 

 of the mud that sticks to their feet, water birds are said to be 

 important carriers of the seeds of water and marsh plants. 



296. Germinating Power of Seeds. The seeds of dif- 

 ferent plants differ greatly in the length of time that they 

 remain able to germinate. As a rule, it is found that seeds 

 germinate best the season after they were produced ; that is, 

 at this time the largest proportion of seeds begin to germinate, 

 the growth of the embryos goes on most rapidly, and they are 

 most likely to grow into full-sized plants. After the first 

 season the germinating power usually diminishes, but at 

 very different rates in different cases. Some seeds will not 

 germinate at all if they are more than a year old ; some 

 remain able to germinate for two or three years, and some for 

 a much longer period. There is no doubt that some kinds of 

 seeds can still germinate when they are sixty or seventy years 

 old, and a few have been found to keep the power of germinat- 

 ing for as long as eighty-five years. There is probably no 

 well-established case in which seeds have germinated at a 

 much greater age than this ; although stories, quite without 

 foundation, are told of seeds that germinated after being 

 buried in the ground for centuries, or after lying for thousands 

 of years in Egyptian tombs. 



The conditions under which seeds have been kept have 

 much to do with their germinating power. For example, 

 they must be kept dry ; for if they become moist they are 

 likely to begin to germinate, and then, qpnditions not being 

 favorable for the completion of germination, the embryos 

 die. The germinating power of most seeds is destroyed by 

 exposure to extreme heat or cold. But to this rule there are 



