Page:Summer - from the Journal of Henry D. Thoreau.djvu/215

Rh confirming my theory. As chemists detect the presence of ozone in the atmosphere by exposing to it a delicately prepared paper, so the lakes detect for us thus the presence of the pine pollen in the atmosphere. They are our pollenometers. How much of this invisible dust must be floating in the atmosphere, and be inhaled and drunk by us at this season! Who knows but the pollen of some plants may be unwholesome to inhale, and produce the diseases of the season, and but it may be the source of some of the peculiar fragrances in the atmosphere which we cannot otherwise account for.

Of course a large pond will collect the most, and you will find most at the bottom of very deep bays into which the wind blows. I do not believe there is any part of this town into which the pollen of the pine may not fall. The time to examine the ponds this year was, I should say, from the 15th to the 20th of this month. I find that the pines are now effete, especially the pitch-pine. The sterile flowers are turned reddish. The flower of the white pine is lighter colored, and all but a very little indeed is effete. In the white pine there is a dense cluster of twenty or thirty little flowers about the base of this year's shoot. I did not expect to find any pollen, the pond was so small and distant from any wood, but thought I would examine.