340 xjBssons wite plants 



or environments, which determine whether the seed 

 can germinate and the plant thrive after dissemi- 

 nation has taken place. The pupil can readily ob- 

 serve how important the factor of environment is by 

 noticing how readily weeds spring up along road- 

 sides, railways, lake shores, and in newly cleared 

 land. If the pupil is fortunate enough to know 

 of a meadow which has been plowed and the 

 land then neglected, let him watch what takes 

 place; or, he may consider why it is that weeds 

 spread more rapidly in gardens than in meadows. 

 423. "While there are evident means by which 

 the seeds of plants are disseminated, as we have 

 now indicated, the pupil must nevertheless be 

 warned that it is easy to overstate the impor- 

 tance of such features. There is too great tendency 

 to endeavor to find a specific use or adaptation 

 for every attribute or structure of a plant, and 

 then to explain its origin by supposing that it 

 came about in order to fulfil such an adaptation. 

 But we really cannot understand plants by inter- 

 preting them solely upon their present or obvious 

 characters: the reasons for the appearing of given 

 attributes should be sought in the genealogy, not 

 in the present -time characteristics. It is possible 

 that many of these structures which seem to us 

 to have arisen for the purpose of dispersing the 

 seeds may have originated as incidental or cor- 



