178 RHAMNACEAE 



tire, several-ribbed leaves and early deciduous stipules. The 

 flowers are perfect or polygamous, axillary, and often clustered 

 in various w^ays. There are 4 or 5 sepals, 4 or 5 petals (the 

 latter sometimes wanting), and 4 or 5 stamens w4th short fila- 

 ments. The ovary is 2- or 4-celled, with 2 or 4 styles united 

 at the base. The fruit is a berry-like drupe which contains 3 to 

 4 nutlets. 



Some 90 species of buckthorn are known in temperate and 

 warmer regions. About 15 of them are native in North 

 America and 3 occur in Illinois. 



Key to the Buckthorn Species 



Flowers with 4 sepals and 4 petals, fruit containing 2 nutlets. 



R. lanceolata, p. 178 



Flowers with 5 sepals and 5 petals, fruit containing 3 nutlets. 

 Pedicels of flowers glabrate, petals absent, nutlets grooved 



on the back R. alnifolia, p. 180 



Pedicels of tiowers pubescent, petals 5, nutlets not grooved 



on the back R. caroliniana, p. 180 



RHAMNUS LANCEOLATA Pursh 

 Lance-Leaved Buckthorn 



The Lance-Leaved Buckthorn, fig. 44, is a small or large, 

 widely branching shrub with gray to dark brown branches. 

 The branchlets, at first puberulent, become smooth or nearly 

 so and gray by the end of the season. The ovate-oblong to 

 ovate-lanceolate leaves are U/4 to 4 inches long by ^ to 1^ 

 inches wide, narrowed or rounded at the base, and acute or 

 acuminate at the apex. Their margins are crenulate-serrate; 

 and the upper surface becomes smooth, but the lower surface 

 remains more or less pubescent. The petioles are definite, 

 though short, and variable in length. 



The dioecious, yellowish-green, fragrant flowers appear in 

 May with the leaves and stand in sessile clusters in the axils 

 of lower leaves. Generally there are 1 to 3, sometimes as many 

 as 6, flowers in a cluster. The pedicels on which they stand 

 are glabrate and quite short. The black fruit, which matures 

 in August and September, is globose, about l/^ inch in diameter, 

 and contains 2 nutlets, each with a deep groove on the back. 



Distribution. — The Lance-Leaved Buckthorn inhabits many 

 types of habitats from very dry ground to bogs. It ranges from 

 Pennsylvania to Nebraska and south to Alabama and Texas. 



