1 52 RUTACEAE 



There are only three species of hop-tree, all natives of the 

 United States and Mexico. Only one of them occurs in Illinois. 



PTELEA TRIPOLI ATA Linnaeus 

 Wafer Ash Hop-Tree 



The Wafer Ash, fig. 35, is an erect, sometimes treelike, 

 shrub 5 to 15 feet tall, with smooth, gray or grayish-brown 

 bark, which may be roughened on old specimens, light to me- 

 dium brown branches and branchlets, and small, 3-foliate, ash- 

 like, compound leaves, which stand on petioles 2|/^ to 4 inches 

 long. The leaflets are sessile or nearly so and are variable in 

 size and shape. They are ovate to oblong-lanceolate, on fruit- 

 ing branches 1^ to 6 inches long, and on sterile shoots often 

 somewhat larger. Lateral leaflets are about two-thirds as 

 large as the terminal one, and all are somewhat inequilateral, 

 the lateral ones the more noticeably so. They are short-acumi- 

 nate and gradually tapered to blunt and often distinctly 

 notched tips and are oblique and narrowed to rounded at the 

 base. The margins, though usually entire, may be undulate or 

 coarsely serrate. The leaf surface at maturity is smooth and 

 shining above and pale and smooth below, and both surfaces 

 are sprinkled with black dots. 



The numerous, small, greenish flowers, which appear in 

 June and early July after the leaves are almost full grown, are 

 borne in panicled cymes. The fruit, which matures in August 

 and September, is a colorless samara about 1/^ to 1 inch long, 

 usually circular but sometimes oval in outline, with a rounded 

 or notched apex and a rounded, subcordate, or sometimes 

 somewhat narrowed base. Both of its faces are strongly and 

 coarsely reticulated, and the sp^aces between veins are sprinkled 

 with resinous glands. The body of the samara is oblong and 

 situated near its center. 



Distribution. — The Wafer Ash, a shrub of limestone bluffs 

 and black alluvial soils along streams, occurs from Connecticut 

 and southern Ontario westward to Wisconsin and south to 

 Florida and northern Mexico. It grows throughout the state 

 of Illinois, wherever suitable habitats occur. 



Individuals with leaflets remaining hairy are segregated as 

 form pubescens (Pursh) Fernald; shrubs of wider growth habit 

 and pubescent branchlets as var. Deamiana Nieuwland. 



