FLORA OF THE DISTRICT OF COLUMBIA. 135 



3. Populus alba L. White or silver poplar. 

 Abandoned nurseries and old fields. March. Native of Eur. and Asia. 



Populus alba bolleana Masters, Bolle's poplar, from Turkestan, is distinguished 

 from the species by its pyramidal form and fastigiate branches. The leaves are larger 

 and more deeply lobed than in the type and the lobes are incisely toothed. 



4. Populus canescens (Ait.) J. E. Smith. Gray poplar. 

 In cultivation and escaped. March. Native of Eur. 



Populus tacamahaca JMill. (P. candicans Ait.; P. balsamifera candicans A. Gray), 

 the Balm of Gilead, is cultivated. Native of northern XJ. S. It is recognized by its 

 broadly ovate, crenulate leaves, 6-20 cm. long, silvery beneath. 



5. Populus heterophylla L. Swamp poplar. 

 Low ground and swamps; above Great Falls (Bartlett). Apr. Eastern states, south 



to Ga. 



35. MYRICACEAE. Bayberry Family. 



Leaves entire or toothed, without stipules; fruit a small drupe, usually covered with 

 wax 1. MYRICA, 



Leaves pinnately lobed, with stipules; fruit nutlike, surrounded by a burlike invo- 

 lucre 2. COMPTONIA. 



1. MYRICA L. 

 1. Myrica carolinensis Mill. Bayberry. 



Pine barrens and swamps; Silver Springs and throughout Prince Georges County; 

 Eastern N. Amer. (if. cerifera of Ward's Flora.) 



2. COMPTONIA Banks. 



1. Comptonia peregrina (L.) Coulter. Sweet fern. 



Near the Reform School; rare. Northern and eastern N. Amer. (Myrica aspleni- 

 folia L.) 



36. JUGLANDACEAE. Walnnt Family. 



Leaflets 11-23, oblong-lanceolate, acuminate; staminate amenta solitary; husk of the 

 fruit indehiscent 1. JUGLANS. 



Leaflets 5-9, unequal, the lower pairs commonly shorter; staminate aments in clusters; 

 husk dehiscent 2. HICORIA. 



1. JUGLANS L. 



Leaflets with an asymmetric base; fruit globose, 4-6 cm. in diameter 1. J. nigra. 



Leaflets with a nearly symmetric base, the terminal leaflet on a stalk 1 cm. long or 

 more; fruit oblong, 4-7 cm. long, 3-4 cm. in diameter 2. J. cinerea. 



1. Juglans nigra L. Black walnut. 

 Rich deciduous woods. Apr.-May; fr. Oct. Eastern U. S. 



2. Juglans cinerea L. Butternut. 

 Rich woods; Potomac valley above Georgetown. Apr.-May; fr. Oct. Eastern N. 



Amer. 



Juglans regia L., the cultivated English walnut, is distinguished by its elliptic- 

 oblong, unequal-sided, entire leaflets. Native of Asia. 



2. HICORIA Raf. 



Rachis of leaves perfectly glabrous. Bud scales numerous, imbricate. 

 Leaflets 3-7, oblong or oblong-lanceolate; fruit obovoid, 4-5 cm. long, the husk 



thin, the nut angled, thick-shelled, bitter 3.. H. glabra. 



Leaflets 5-7, oblong or ovate-lanceolate; fruit globose or nearly so, 2.5 cm. in diame- 

 ter or less, the husk thin, the nut not angled, thin-shelled, sweet. 



4. H. microcaipa. 



