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 Epilobium spicatum in the newest clearings, 

 which is dichogamous (proterandrous) to a degree which 

 practically forbids self-fertilization ; and in older fields, .4s- 

 clepias Cornuti, which is specially adapted for cross-fertiliza- 

 tion by flying insects ; Antennaria plantaginifolia and A. 

 margaritacea, which are dioecious ; and next to these per- 

 haps the two wild Strawberries, then Erigeron annuum and 

 E. strigosum, with certain Asters and Goldenrods, all insect- 

 visited and dichogamous, and Verbena hastata, V. urticifolia, 

 etc., 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. 



