COMPOSITAE TUBULIFLORAE 



763 



Fig. 440a. Boneset (Eupatorium altissimum L.) Common in the Mississippi valley. 

 At the right Maximilian's Sunflower (Helianthus Maximillani) common in Mississippi val- 

 ley. (Charlotte M. King). 



Iva L. Marsh Elder 



Herbaceous or some shrubby plants, pistillate and staminate flowers in the 

 same head. The lower leaves opposite, the upper alternate; flowers greenish, 

 rays absent; subtended by an involucre of hemispherical or cup-shaped bracts; 

 achenes obovoid or lenticular, without pappus. 



About 12 species of western and southern America. 



Iva axillaris Pursh. Small-flowered Marsh-elder 



A smooth or sparingly pubescent perennial with herbaceous stems, from 1-2 

 feet high, with woody roots; leaves sessile, entire or nearly so; obovate, oblong 

 or linear oblong, the lower opposite, the upper smaller and alternate ; heads gen- 

 erally solitary in the axils of the leaves, short petioled, involucre hemispherical, 

 pistillate, flowers with tubular corolla. 



Distribution. Common especially in the saline soils from Nebraska to the 

 Dakotas, British Columbia, California and New Mexico. 

 Iva xanthifolia Nutt. Marsh Elder 



An annual from 1-8 feet high; stem frequently pubescent when young; all 

 the leaves opposite, rhombic, ovate or the lowest heart-shaped, doubly serrate 

 or cut-toothed, obscurely lobed; the upper surfaces minutely scabrous, canescent 

 beneath, especially when young; petiole frequently ciliate at its upper end; 

 flowers born in spike-like clusters forming a compound panicle; heads small, 

 crowded; outer bracts of the involucre broadly ovate, greenish; inner mem- 

 branaceous; achenes glabrate. 



