220 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



1. NYSSA L. 

 1. Nyssa sylvatica Marsh. Black gum. 



Rich soil, usually along streams or swamps, but sometimes on hillsides or in dry 

 fields; abundant. May. Eastern U. S. {N. multiflora Wang.) 



The plants sometimes flower when only shrubs. Leaves bright crimson in autumn; 

 fruit nearly black, juicy, with a single ridged stone. The leaves are usually entire, 

 but on young trees are sometimes toothed. 



2. CORNtrs L. Dogwood. 



Flowers in dense heads, surrounded by large white petal-like bracts; trees; fruit red. 



1. C. florida. 

 Flowers in cymes, without petal-like bracts; shrubs; fruit blue or white. 



Leaves alternate. Fruit blue 2. C. altemifolia. 



Leaves opposite. 



Leaves downy-hairy beneath, with white or rusty brown hairs. Fruit blue. 



Leaves broadly oval or rounded, ovate, white-hairy beneath 3. C. rugosa. 



Leaves ovate or ovate-oblong, with mostly rusty brown hairs beneath. 



4. C. amomum. 

 Leaves glabrous beneath, or with closely appressed white hairs. 



Branches purple; leaves short-pointed; cymes dense, flat 5. C. stolonifera. 



Branches gray; leaves taper-pointed; cymes loosely flowered, convex. 



6. C. femina. 



1. Comus florida L. Flowering dogwood. 

 Woods or dry hillsides; abundant. Apr.-May. Eastern U. S. (Cynoxylum fiori- 



dum Raf.) 



The large white bracts are often mistaken for petals. A form with pink bracts is 

 frequent in cultivation. A flowering branch is shown in plate 35. 



2. Comus alternifolia L. f. Blue dogwood. 

 Above the Aqueduct Bridge, May, 1877 {Ward). Eastern N. Amer. 



3. Comus rugosa Lam. 



Dodge's Mill, 1883 ( W. P. Conant) . Eastern N. Amer. (C. circinata L'Her.) 



4. Comus amomum Mill. 



Low woods and along streams; common. May-June. Eastern N. Amer. (C. 

 sericea L.; C. stolonifera of Ward's Flora, in part.) 



5. Comus stolonifera Michx. 



Low ground along the upper Potomac; infrequent. Widely distributed in N. 

 Amer. 



6. Comus femina Mill. 



Swamp near Hyattsville, May, 1910 (McAtee). May-June. Eastern U. S. (C. 

 paniculata L'H6r.) 



117. CIETHRACEAE. Sweet alder Family. 



1. CLETHBA L. 

 1. Clethra alnifolia L. • Sweet alder. 



Swamps in the Coastal Plain; infrequent; Hollywood Swamp; Powder Mill swamps. 

 July-Aug. Coastal Plain from Me. to Fla. 



118. PYROLACEAE. SMnleaf Family. 



Flowers in an umbel; leaves sharply serrate l.CHIMAPHILA 



Flowers in a raceme; leaves entire or obscurely crenate 2. PYROLA 



