18 CONTRIBUTIOIsrS FROM THE NATIONAL, HERBARIUM. 



connect Washington with Great Falls (PI. 8B). They pass along the 

 high land skirting the heads of the ravines, one on the Maryland side, 

 the other on the Virginia side. By taldng the trolley to a station 

 near the head of a ravine on the south side, one can make a trip down 

 the ravine to the river, along the steep bank of the river to the next 

 ravine, and, ascending this, return by trolley. On the north side 

 one may do the same, or the return can be made along the road or 

 towpath to Cabin John. There are four larger ravines below Great 

 Falls on the south side: Difficult Run (PI. 4), BuUneck Run, Scotts 

 Run, and Dead Run. Farther down is Pimmits Run, which enters 

 the main valley near Chain Bridge. On the north side a pleasant 

 trip can be made by getting off the trolley at Ferndale and going 

 down Cabin John Run to Cabin John Bridge. 



The Chesapeake and Ohio Canal extends from Georgetown to Great 

 Falls and on to Cumberland, following the left bank of the Potomac. 

 The flora along the canal is of especial interest, as the original species 

 have been preserved from destruction by animals and from the 

 encroachment of agricultural operations and residential sections. 

 In the water of the canal and along the margin are numerous aquatic 

 and semiaquatic plants. The cliffs and banks are the home of many 

 species that are not easily accessible elsewhere. The towpath of the 

 canal offers to the pedestrian the most convenient road for observing 

 the plants of the Potomac Valley. (PI. 8A). 



Spring flowers are abundant in the valleys and on the alluvial slopes 

 (PI. 9). The earliest species of interest to the layman is the hepatica, 

 soon followed by the bloodroot. Several weedy species with in- 

 conspicuous flowers bloom earlier in the season, or even during 

 the winter months, when the weather is warm, or when growing 

 in especially sunny or protected spots. The skunk cabbage, the 

 earliest of the strictly spring flowers, is found widely distributed in 

 oiu" area in moist places, mostly in the woods. Other herbaceous 

 species with showy flowers blooming in early April are the spring 

 beauty, trout lily, wake-robin, twin-leaf, blue violet {Viola sororia 

 and V. papilionacea) , cream violet (F. striata), Dutchman's breeches, 

 buttercup {Ranunculus septentrionalis and R. hispidus), pepper-root 

 {Dentaria lieteropJiylla and D. laciniata), harbinger-of-spring, bluebells, 

 Saxifraga virginiensis, and Alsine puhera. A httle later, usually the 

 latter part of April, will be found Phlox divaricata, wild ginger, 

 Jack-in-the-pulpit, columbine, golden ragwort, and cranesbill. 



Among the woody plants the soft maple and the elms flower very 

 early, often in February and March. The red maple, ashes, box- 

 elder, and the catkin-bearing trees flower in April or early May. 

 The redbud with red flowers and the June berry with white flowers 

 are conspicuous in the woods before the trees produce their leaves. 

 Somewhat later, but before the forest has come into full leaf, the 



