120 THE BIOLOGY OF THE SEASONS 



flowers, but perhaps they may indicate the risk there is 

 of exaggerating a truth till it becomes false. 



In support of the generally accepted view that brightly 

 coloured petals are attractive " signs " which draw customers 

 to the floral " Gasthaus," there is a multitude of observations 

 as to the frequency of visits paid by particular insects to par- 

 ticular flowers. It is instructive to give a holiday afternoon 

 to watching, for instance, how one of the big humble-bees (e.g. 

 Bombus hortorum) behaves on a flower-covered bank. She is 

 so extraordinarily selective. And as we see this, it sends a 

 thrill through us to remember that Aristotle watched the 

 same sort of thing more than two thousand years ago. In 

 his Natural History it is written : "A bee, on any one 

 expedition, does not pass from one kind of plant to another, 

 but confines itself to a single species for instance, to violets 

 and does not change until it has first returned to the hive." 

 After more than two thousand years, the botanist Kerner 

 von Marilaun, who wrote one of the most living of all the 

 botany books, watched not the hive-bee, but Bombus 

 montanus in an Alpine valley. He saw it visiting only 

 Anthyllis alpestris, and passing over Pedicularisjacquini and 

 P. incarnata ; while in another valley the same species of 

 bee buzzed from one Pedicularis blossom to another, and 

 passed over the Anthyllis attractions. 



We have now a perfectly precise and rapidly growing 

 record of the habitual pollinators of particular flowers, 

 and there has already been more than one good example of 

 a truly biological (or oecological, if you like) student's 

 '' Flora," which tells for each plant, not only its diagnostic 

 characters, but its welcome and unwelcome insect-visitors, 

 its gall-producers (if it has any), its parasites, its seed- 

 distributors (if it has any), its characteristic environment, 

 and it? plant associates. In hoc signo laboremus. 



Corroborations come also from wide outlooks, in which 



