Disi'KRsiox or FRrns axd seeds 233 



ducts of their cones on hare tracts of land. The 

 liL,ditest of all tree seeds is that of the birch ; it is 

 gifted with two winL;s or nicnihranes, so that it 

 floats in the air before the lij^htest breeze, and this 

 ma\' account for tlu- widt' distribution of the tree 

 which has been found l; rowing; from Mount Mtna 

 to Iceland and Greenland. I ma)' i^ive an instance 

 of a common which, twent)- }'ears ae^o, was co\ercd 

 onl)' b\- fur/.e, broom, and brake-fern ; about four- 

 teen )-ears since, a shower of birch seed must have 

 been strewn over the j^round, and now it has be- 

 come a wood, shuttiuL^ out the distant \iews and 

 quite alterinsT the character of the land.scape. 



The wind again is the agency for the dispersion 

 of the seeds of such plants as the common ground- 

 sel ; here it ma\- not be iminteresting to note the 

 beautiful pro\ ision made in regard to the buoyanc\- 

 of the seeds. These winged structures which the 

 wind so lightl)' blows into the air must attain a 

 certain altitude from which the\' can be success- 

 full)- launched, and therefore we fmd that a large 

 class of low-growing plants ha\e their seeds fur- 

 nished with accessories in the form of light silky 

 down or hairs. 



