HORSETAILS 157 



tufts of fibrous roots from its nodes, and the bright green 

 leaves, or fronds, about 2 or 3 inches long, also rise from 

 the nodes in tufts. They display crozier-like curling 

 (circinate vernation) in their young condition, but at 

 maturity they are erect. The fructifications (sporo- 

 carps) are globular, about | inch in diameter; they 

 appear like little pills attached by very short stalks to 

 the bases of the leaves. These sporocarps are four- 

 chambered, and in each chamber there is a single sorus 

 containing both mega- and micro-sporangia. The 

 spores are in due course liberated; they develop into 

 male and female prothalli. This plant is often over- 

 looked ; it ranges in Europe north of the Alps ; it is rare 

 in Ireland, but widely distributed over Scotland and 

 England. 



In these heterosporous plants we detect a step in the 

 direction of that marked elaboration of sex exhibited 

 in the pistil and stamens of flowering plants; but this 

 step is better demonstrated in other Pteridophytes, as 

 we shall see, and there is good reason to believe that the 

 Water Ferns are a side-line of plant-life, leading to no 

 forms higher than themselves. 



Equisetales: Horsetails. 



Plants of this group are not likely to be overlooked; 

 they are familiar even to children, and the agriculturalist 

 knows them as pests which are none too easy to eliminate 

 once they have obtained a local habitation in his ground. 

 Equisetum arvense, for example, develops a branched 

 rhizome — i.e., an underground stem — that penetrates 

 to a depth in the soil at which it usually succeeds in 



