iv PURSUIT OF KNOWLEDGE 79 



made a sketch of the fish which he believed would live 

 at the time this geological stratum was formed. He did 

 not understand the cheer with which his drawing was 

 received by the company, until someone brought forward 

 an actual fossil specimen which had just been found and 

 showed that it agreed perfectly with the sketch which 

 Agassiz had created from his own knowledge of what 

 characteristics a fish belonging to a particular stratum 

 ought to possess. 



Facts known to everyone often have to wait hundreds 

 of years before their true significance is understood. A 

 remarkable instance of this is the relation of the flower 

 of a plant to the fruit which follows it. In very early 

 days men must have noticed that when the blossom on 

 a tree or bush was destroyed no fruit could be expected 

 from it. First the flower, then the fruit, has been a 

 matter of common knowledge from time immemorial, 

 yet the causal relationship between the two stages was 

 not established until the seventeenth century. Hero- 

 dotus, in the middle of the fifth century B.C., had 

 observed that in Assyria the female tree of the date- 

 palm was made fertile by dusting it with the branches 

 of the male, but he did not pursue his inquiries any 

 further. Other Greek philosophers who followed him 

 taught that fertilisation is unnecessary, that both male 

 and female date-palms bear fruit, and held like beliefs 

 which a single experiment would have shown to be 

 erroneous. So it was with other plants ; nothing was 

 accurately known of the functions of the various parts 

 of the flower concerned in the production of the fruit, 

 and no serious attempt had been made to secure precise 

 knowledge. 



If a common apple blossom be examined, slender 

 filaments or stamens will be seen bearing golden pollen 



