This section is from the book "Woody Plants In Winter", by Earl L. Core, Nelle P. Ammons. Also available from Amazon: Woody Plants in Winter.
Deciduous trees with milky sap. Twigs moderate, rounded; pith moderate, round, continuous. Buds sessile, solitary or multiple, ovoid, oblique, with 3-6 scales; end-bud lacking. Leaf-scars alternate, round or half-round; bundle-traces numerous, scattered or in 3 groups; stipule-scars narrow.

Fig. 87. Morus rubra.

Fig. 88. Morus alba.
a. | Buds elongated, 6-8 mm. long, somewhat spreading | 1. | M. rubra |
a. | Buds triangular-ovoid, short and closely appressed | 2. | M. alba |
1. M. rubra L. Red Mulberry. A tree 5-20 m. high, up to 2 m. in diameter; bark brown and rough; twigs often downy; buds spreading, 6-8 mm. long; bud-scales brown-margined. Rich woods, Ontario to Minnesota and South Dakota, south to Florida and Texas (Fig. 87).
2. M. alba L. White Mulberry. A small tree, sometimes 14 m. high and 1 m. in diameter; bark light gray, rough, the branches spreading; buds appressed, 3-4 mm. long; bud-scales generally uniformly colored. Introduced from Europe, much spread from cultivation and naturalized (Fig. 88).
 
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