160 NATURE TEACHING 



according 1 to how windy it is, settle down on the 

 ground. 



Similar observations should be made on the thistle, 

 lettuce, goafs-beard or salsify, willow-herbs, etc. The 

 details will vary in each case, but all are alike in possess- 

 ing some means of enabling their seeds to be readily 

 blown about by the wind. Additional evidence can be 

 obtained by going on a dry windy day in summer to a 

 piece of waste ground which has a lot of thistles growing 

 on it, and watching the thistle-down blowing about. 

 Collect some pieces of thistle-down and note the small 

 seeds attached to them. Then recollect that each little 

 piece of thistle-down is probably carrying one seed, and 

 you will understand how thistles are often such trouble- 

 some pests to farmers, and why it is so important that 

 they should be cut down before and not after they have 

 flowered. 



Take a ripe pine-cone. Pick out the seeds from 

 -amongst the scales, and note that each is provided with 

 <a thin wing or sail. 



Examine also the seeds of the white birch. These 

 are very small, and each is provided with a delicate thin 

 wing. In many localities near London and elsewhere, 

 numerous instances will be seen of young birches coming 

 up on waste lands, a result due very largely to their 

 effective method of seed dispersal. 



Examine ripe fruits of the maple and ash " keys." 

 Both of these have wings by which they are blown about 

 by the wind. Cut some open and see the seeds inside. 

 In the pine and birch the seed itself had a wing, whilst 

 in the maple and ash, it is the fruit which is vyinged, 



