THE AMERICAN BOTANIST. 6T 



wonder wh\' all flowers are therefore not apetalous. Evi- 

 dently the reason they are not is becaUvSe some of them 

 have found petals useful. It is fairly certain that the first 

 flow^ers had no petals, but in one way or another a large 

 majority have since acquired them, until now^,froiTi at first 

 being merely useful to the plants, they have become so iin- 

 portant to certain species that they may be said to be ab- 

 solutely essential to their existence. 



In the closing of flov^'ers at night and in cold or stormy 

 weather, we see how the petals act as a protection to the 

 tender essential organs. The grape seems to require its 

 petals for this use alone, for the corolla never expands. 

 When the flower blooms or "opens" the petals simply fall 

 to the ground. Other flowers seem to need their petals 

 principalh' for the attraction of insects. They encourage 

 their visits in order to secure cross-pollination and do not 

 spread their man\^ colored petals in vain, for the insects 

 have learned that food is to be obtained at the sign of the 

 brilliant corolla and are sure to visit it. In plants whose 

 flowers are borne in close clusters we may often see indica- 

 tions of plant frugality in the matter of advertising. Thus 

 in the wild carrot or Queen Anne's lace, while the great 

 majoritj^ of the flowers have small petals, those on the 

 outer edges of the chisterhave their petals much increased 

 in size, this advertisement serving the whole cluster. The 

 same feature is noticeable in the hobble-bush {Viburnum 

 lantanoides) though in this case the outer flowers are al- 

 most all corolla. So much vigor has been used up in co- 

 rolla making that the essential organs in these flowers are 

 functionless. A still more familiar example is found in the 

 great composite family in which the showy "rays" are 

 formed of the enlarged petals of the flowers in the outer 

 circle while the other flowers in the center have small and 

 inconspicuous corollas designed strictly for business. The 

 sunflower, daisy and aster are good types of this. 



The most important use of the petals, however, is not 

 in attracting insects to the nectar but in controlling their 

 motions while they are getting it. We have seen that 



