Cornus Cornaceae 729 



6151. NYSSA L. 

 [Fernald. The varieties of Nyssa sylvatica. Rhodora 37: 433-437. 1935.] 



Lower surface of leaves smooth, not papillate or rarely so, glabrous, glabrate, or rarely 

 densely pubescent on young specimens; leaves firm or subcoriaceous when mature, 

 short-acute or blunt at the apex, lustrous above; green branchlets usually bending 

 when flexed to a right angle; wood difficult to split 1. N. sylvatica var. typica. 



Lower surface of leaves papillose, glabrous, glabrate or more or less pubescent, espe- 

 cially on the veins; leaves not firm or subcoriaceous when mature, usually acumi- 

 nate at the apex or some blunt; green branchlets usually breaking when flexed 

 to a right angle; wood easy to split la. N. sylvatica var. caroliniana. 



1. Nyssa sylvatica Marsh, var. typica Fern. Black Gum. Map 1552. 

 Infrequent to rare in the northern two thirds of the state and frequent to 

 common in the southern part. It is found in both dry and wet soils, ap- 

 parently preferring slightly acid soils. It is erratic in its distribution and 

 is found in several tree associations. The leaves of coppice shoots and some- 

 times those of seedlings are often more or less lobed. 



West-cent. Maine, s. Ont., s. Mich., se. Wis. to n. Mo., southw. to Fla. 

 and ne. Tex. 



la. Nyssa sylvatica var. caroliniana (Poir.) Fern. Map 1553. This 

 variety is infrequent in the southern part of the state. It is one of the cove 

 type and prefers a richer soil than does the typical form. Pioneers have 

 always insisted that there were two kinds of black gum. They distinguish 

 them by their splitting qualities. The form very difficult to split was 

 known as the black gum, and the form that split "like poplar" was known 

 as yellow gum. The bark of the variety much resembles that of the tulip 

 tree, and the branches are usually ascending. 



Chester County Pa. to Essex County, Ont., southw. to N. C, Miss., and 

 e. Tex. 



6159. CORNUS [Tourn.] L. 



Inflorescence capitate, surrounded by a large 4-leaved, white, petaloid involucre; fruit 

 red. 



Plants subherbaceous, low, mostly less than 2 dm high 1. C. canadensis. 



Plants arborescent, small trees 2. C. florida. 



Inflorescence cymose, without an involucre; fruit not red. 

 Pith of branchlets and of one and two year old branches white. 



Leaves alternate 3. C. alternifolia. 



Leaves opposite. 



Leaves broadly ovate, generally having 7-9 pairs of veins, usually woolly- 

 pubescent beneath at maturity; branchlets yellow green and usually more 

 or less blotched with longitudinal, purplish spots ; fruit bluish . . 4. C. rugosa. 

 Leaves ovate, oblong-ovate or lanceolate-ovate, generally having 3-6 pairs of 

 veins, woolly or appressed-pubescent beneath at maturity; branchlets 

 reddish or grayish. 

 Under surface of leaves mostly woolly at maturity. 



Leaves not rough above; pith of last year's branchlet wide, more than a 



third the diameter of the branchlet ; branches bright red 



5a. C. stolonifera var. Bailey i. 



Leaves rough above; pith of last year's branchlet small, usually less than a 

 third the diameter of the branchlet ; branches gray (this species rarely 

 with a white pith) 6. C. asperifolia. 



