SEEDS. 19 



of their development bring the micropyle into such a 

 position as to favor the entrance of the pollen tube. 

 Again, the hairy appendages of numerous achenia, such 

 as those of the dandelion and related plants, are so placed 

 as to bring the radicle on the lower side as the object 

 alights on the surface of the ground.^ Such adaptations 

 are of so constant occurrence that the student can hardly 

 fail to receive the impression, in general a correct one, 

 that the simplest structural facts are likely to have some 

 important physiological significance. On the other hand, 

 there are numerous cases of " accidental " peculiarities, for 

 which no reason is manifest, and which at present are not 

 explained. 



1 Cf. Eowlee, I.e. 



