72 THE STORY-BOOK OF SCIENCE 



middle of which are the seeds. If the air is calm, 

 this down piles up at the foot of the tree in a bed of 

 cotton wool, as white as snow ; but at the least breath 

 of wind the flakes are borne long distances, carry- 

 ing with them the seeds, which thus find unoccupied 

 places where they can germinate and become trees. 

 Many other seeds are provided with soft aigrettes, 

 silky plumes, which keep them up in the air a long 

 time and permit them distant journeys in order to 

 disseminate the plant. For example, who is not 

 familiar with the seeds of thistles and dandelions, 

 those beautiful silky plumed seeds that you take 

 pleasure in blowing into the air?" 



"Can the flock of poplar bolls be put to the same 

 use as cotton ?" Jules asked. 



"By no means. There is too little of it, and it 

 would be too difficult to gather. Besides, it is so 

 short it might not be possible to spin it. But if we 

 ourselves cannot make use of it, others find it very 

 useful. This flock is the little birds 7 cotton; many 

 gather it to line their nests. The goldfinch, among 

 others, is one of the cleverest of the clever. Its 

 house of cotton is a masterpiece of elegance and 

 solidity. In the fork of several little branches, with 

 the cottony flock of the willow and poplar, with bits 

 of wool that hedge thorns pull out from sheep as 

 they pass, with the plumy aigrettes of thistle seeds, 

 it makes for its young a cup-shaped mattress, so soft 

 and warm and wadded that no little prince in his 

 swaddling-clothes ever had the like. 



"To build their nests, birds find materials near 

 at hand; they only have to set to work. When 



