DESCRIPTIONS OF SOME COMMON WEEDS 



233 



rforseweed (Erigeron canadensis, L.). A bristly hairy 

 annual from one to five feet high with erect stems, 

 leaves linear, mostly entire, the root leaves cut-lobed. 

 Heads very numerous, small cylindrical in panicles. A 

 common weed in waste places across the continent, also 

 in Europe. Fields and gardens. 



Low Horseweed (Erigeron divarica- 

 tus, L.) is a diffuse spreading plant 

 with purple ray-flowers ; common in 

 sandy, gravelly soil from Indiana and 

 Nebraska southward ; it is sometimes 

 a troublesome weed. 



Marsh Elder (Iva xanthifolia, 

 Nutt.). A tall, rough annual one to 

 eight feet high ; leaves opposite and 

 hairy, rhombic, the lowest sometimes 

 heart-shaped, cut-toothed or doubly 

 serrate ; flowers in axillary clusters on 

 ample terminal panicles; heads small. 

 crowded; outer bracts of the invo- 

 lucre broadly ovate, greenish ; inner 

 membranaceous ; achenes smooth. A 

 weed that is recognized as of consid- 

 erable importance in the corn fields in 

 the western part of the state ; occurs 

 frequently in Nebraska, Kansas -and 



Colorado. In Iowa generally confined 



, , , ., j , , Fig. 146. Horseweed 



to barnyards and railroad embank- (Erigeron canadensis). 

 ments. 



Small-flowered Marsh Elder (Iva axillaris, Pursh). A 

 smooth or sparingly pubescent perennial with herbaceous 

 stems, from one to two feet high, with woody roots ; 

 leaves sessile, entire or nearly so ; obovate, oblong or 

 linear-oblong, the lower opposite, the upper smaller and 

 alternate, short petioled ; heads generally solitary in the 

 axils of the leaves; involucre hemispherical, pistillate; 



