Class XXL Order V. 



The Alder grows in wet grounds, and forms large thickets 

 jn swamps and about the edges of streams and ponds. Consid- 

 ered as a tree it ranks with those of the smallest size. Its 

 leaves are oval or inversely ovate, serrate, acute, or slightly 

 acuminate, furnished underneath with prominent, parallel, 

 hairy veins. Barren aments pendulous. Fertile ones short, 

 rigid, forming a persistent cone. March, April. 



PENTJ1NDRIJ}. 



254. XANTHIUM. 

 XANTHIUM STRUMARIUM. L. Sea Burdock. 



Stem unarmed ; leaves heart-shaped, three 

 nerved. L. 



A very rough plant, growing at the edges of beaches, Sec. 

 near the salt water. Stem erect, spotted, bristly. Leaves hard 

 and rough like a file, heart-shaped, serrate, on long petioles. 

 The fruit is an oval burr, or nut of two cells, covered with siifV 

 thorns, and ending in a pair of strong points, like horns. Au- 

 gust. 



255. AMBROSIA. 



AMBROSIA ELATIOR. L. Tall Jlmlrosia. Roman Worm- 



wood. 



Leaves twice pinnatifid,, smoothish, petioles cil- 

 iated ; racemes terminal, panicle d , stem wand like. 

 Willd. 



A troublesome weed in cultivated grounds, hardly entitled 

 to the character, which its name might imply. Stem erect, 

 branching, from one to three feet high. Leaves bipinnat- 

 ifid, the upper ones pinnatifid, with parallel segments gradual- 

 ly decreasing in length toward the point. Barren flowers nod- 

 ding, small, in terminal racemes. Fertile flowers lower down, 



