ECOLOGY OF FLOWERS 369 



III 



25. Yarrow .... Achillea millefolium Mull. 



26. Oxeye daisy . . . Chrysanthemum Leucanthemum . . . Mull. 



27. Dandelion . . . Taraxacum officinale . . . Mull., Newell. 



IV 



28. Barberry .... Berberis vulgaris Lubbock. 



29. Mountain laurel . Kalmia latifolia Gray. 



30. White clover . . . Trifolium repens Mtill. 



31. Red clover . . . Trifolium pratense Mull. 



32. Locust Eobinia Pseudacacia Gray. 



33. Wistaria .... Wistaria sinensis Gray. 



34. Vetch Vicia cracca Mull. 



35. Pea , Pisum sativum Mtill. 



36. Bean Phaseolus vulgaris Gray. 



37. Ground-nut . . . Apios tuberosa Gray. 



VI 



38. Partridge-berry . . Mitchella repens Gray. 



39. Primrose .... Primula grandiflora, P. officinalis . Lubbock. 



40. Loosestrife . . . Lythrum Salicaria Gray. 



VII 



41. Milkweed. . . , Asdepias Cornuti .... Mtill., Newell. 



VIII 



42. Lady's-slipper . . Cypripedium acaule Newell. 



439. Cleistogamous Flowers. In marked contrast with 

 such flowers as those discussed in the preceding sections, 

 which bid for insect visitors or expose their pollen to be 

 blown about by the wind, are certain flowers which remain 

 closed even during the pollination of the stigma. These 

 flowers are called cleistogamous and of course are not 



