304 



STRUCTURE OF EQUISETUM 



The stems are of two kinds, subterranean rhizomes that branch 

 extensively through the soil, and aerial stems that arise as 

 branches from the rhizomes. The aerial stem is simple or 

 branched and is characterized by nodes made conspicuous by the 



FIG. 232. A common horsetail fern, Equisetum arvense: a, the green 

 branching plant that lives through the summer /_, scale leaves ; r, rhizome 

 or underground stem with tuberous storage organs, b, early spring shoot 

 that bears a spike or strobilus of modified spore-bearing leaves, sp. This 

 stem is of a light brown color and withers after the spores are shed. H. 

 O. Hanson. 



sheathing teeth-like leaves and strongly furrowed internodes. In 

 such species as branch, these organs originate with great regular- 

 ity in the axils of the leaves and perforating the sheathing leaves 



