THE AMERICAN BOTANIST 143 



from trees. The early vegetation of the earth appears to have 

 been almost entirely arborescent and the herbs are newcomers 

 on the planet. Although the "age and area" hypothesis will 

 not apply in all cases it may be of use in comparing two species 

 with equally effective means of dispersal. In such cases the 

 one with the greatest range might properly be regarded as the 

 oldest. 



Honey-bee Pollinating Ambrosia. — During certain 

 early morning walks in the beginning of August at Green- 

 castle, Indiana. I had occasion to observe the part played by 

 the honey-bee in the pollination of Ambrosia, which struck me 

 as peculiarly interesting. On these particular mornings, about 

 7 a. m., the air was very warm and still. Where the road 

 traversed a certain declivity in the lee of a hedge of tall osage 

 orange it was fringed on one side by a dense growth of 

 Ambrosia triiida, the common rag-weed, and on the opposite 

 side by Ambrosia artcmisiacfolia, the smaller rag-weed. The 

 honey-bees were particularly numerous about the flowers of 

 the ambrosias and I noticed that as a bee would hover close 

 to the long dense staminate flower-clusters the masses of yellow 

 pollen were blown out in clouds by the fanning of the bee's 

 wings. Whenever a bee attempted to alight on a flower-cluster 

 heaps of pollen were jarred loose as the bee struck the stalk. 

 The air being very still the clouds of pollen settled gently down 

 on the foliage and on the pistillate flowers in the upper leaves. 

 much of the pollen floating off and falling upon the neighbor- 

 ing plants, cross-pollination being thereby effectually brought 

 about. As I gazed over the whole patch of rag-weed against 

 the sunlight, puffs of pollen could be seen here and there where 

 the bees were among the flowers. It seemed to me that the 

 honey-bee in this case acted as a very efficient agent of pollina- 

 tion, all the more so as the rag-weeds are adapted more espec- 

 ially to wind-pollination. A few days later when a wind was 

 blowing hardly a bee was to be seen among the rag-weeds. 



