10 ILLUSTRATIONS. 



20A. Showy orchis (Orchis spectabilis). Widely distributed in rich woods in 



late spring, but not abundant. Flowers pink and white. 

 20B . Moccasin flower ( Cypripedium acaule) . A characteristic plant of sandy 



pine woods in May, the saclike lip rosy purple, mottled. 

 21. Lizard's-tail (Saururus cemuus), in a swamp near Dyke. A characteristic 



summer marsh plant with white flowers. 

 22A. Pin oak (Quercus palustris) in May, the leaves partially developed. The 



decurved lower branches are characteristic of this species. 

 22B. Red oak (Quercus maxima) in May. 



23. White oak (Quercus alba) in May, a last year's growth of Andropogon 



elliottii in foreground. 



24. Yellow pondlily (Nymphaea advena) in shallow water near Dyke. Abun- 



dant in the marshes of the Eastern Branch and the lower Potomac. 

 25A. Hepatica (Hepatica americana). Common in rich woods in March and 



April. Our earliest showy spring flower. 

 25B. Cream violet (Viola striata). Low woods along the Potomac in April 

 and May. 



26. May-apple (Podophyllum peltatum), common in rich woods in spring; 



flowers white. Below is the three-leaved stonecrop (Sedum ternatum), 

 frequent in rocky woods; flowers white. 



27. Sassafras (Sassafras variifolium) , as it occurs along old fence rows in the Oxon 



Run valley. 

 28A. Bloodroot (Sanguinaria canadensis); common in rich woods in March 



and April. One of our earliest spring flowers; petals waxy white; 



juice of plant orange-red. 

 28B. Twin-leaf ( Je/ersonia diphylla); rich woods on islands of the Potomac 



in April. Leaves split into two equal parts; flowers white. 

 29A. Dutchman's breeches (Bikukulla cucullaria). Rich woods along the 



upper Potomac in April; flowers white, tinged with pale yellow. 

 29B. Squirrel com (BikuJculla canadensis) . Resembling Dutchnian's breeches 



but less common ; flowers white, tinged with pink. 

 30A. Pepper-root (Dentaria laciniata). Moist woods in April and May, the 



flowers white or pinkish. 

 SOB. Saxifrage (Saxifraga virginiensis) . Common in rocky woods in April; 



flowers white. 

 31 A. Wild strawberry (Fragaria virginiana). Common in fields and open 



grassland in May; flowers white. 

 31B. Star chickweed (Alsine pubera). Common in April and May in rocky 



woods, the flowers white. 



32. Goat's-rue (Cracca virginiana) ; woods near Great Falls. Common in sandy 



or rocky woods in May and June. 



33. Black locust (Robinia pseudo-acacia) in May, just as the leaf buds are open- 



ing. An abundant, probably naturalized tree with handsome racemes 



of white fragrant flowers in early summer. 

 34A. Squaw-root (Conop/toZis americana). Rich woods in May. A brownish 



root parasite, four to eight inches tall. 

 34B. Prickly pear (Opuntia vulgaris), on rocks at Plummers Island. This 



specimen shows the fruit; the yellow flowers appear in June. Our 



only native cactus. 

 35. Flowering dogwood ( Comus florida) . A small woodland tree, the white 

 petal -like bracts conspicuous in the spring before the leaves appear. 



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