242 ESSAYS. 
herbs which under new conditions, have propagated most 
abundantly and rapidly, and competed most successfully in 
the strife for the possession of fields that have taken the 
place of forest. The most aggressive of these in the North- 
ern States are ELpilobium spicatum in the newest clearings, 
which is dichogamous (proterandrous) to a degree which 
practically forbids self-fertilization ; and in older fields, As- 
clepias Cornuti, which is specially adapted for cross-fertiliza- 
tion by flying insects; Antennaria plantaginifolia and A. 
margaritacea, which are diccious; and next to these per- 
haps the two wild Strawberries, then Hrigeron annuum and 
E. strigosum, with certain Asters and Goldenrods, all insect- 
visited and dichogamous, and Verbena hastata, V. urticifolia, 
ete., the frequent natural hybridization of which testifies to 
habitual intercrossing. 
Those who suppose that only conspicuous or odorous flowers 
are visited by flying insects should see how bees throng the 
small, greenish, and to us odorless blossoms of Ampelopsis or 
Virginia Creeper and of its Japanese relative. 
