50 THE HORSETAILS. 



with impunity, though- when cut with the hay it has 

 been found to be quite poisonous to horses. At the 

 first hard frost in autumn, the stems in exposed places 

 perish, but where protected by vegetation they may 

 exist for some time longer. 



- This species is so widely distributed that the cultiva- 

 tor of the fern allies seldom has to transplant it to his 

 grounds ; but if it be desired to make it grow, nothing is 

 easier. A bit of the root-stock, planted almost any- 

 where, will soon produce one of its characteristic thickets. 

 Once started, it is most tenacious of life, and if buried 

 six feet or more in loose soil will ultimately come to the 

 surface again. 



"The Ivory Horsetail. 



It is a curious coincidence that the commonest species 

 in both groups of Equisetum should each be related to a 

 second species that very much resembles it except in 

 size. The great scouring-rush is so near like the com- 

 mon one that it may be doubted whether the two are 

 not forms of a single species; but In the case of the 

 field horsetail and its gigantic counterpart no such 

 uncertainty exists. The difference in size alone would 

 almost be sufficient to distinguish them, for the sterile 

 fronds of this giant species, the ivory horsetail {Equisetum 

 tclmateid], often reach a height of ten feet. Otherwise 

 the two have many points of general resemblance, though 

 none are sufficiently close to cause confusion in identify- 

 ing them. Both are among the earliest of spring plants 

 and are able to grow in a variety of situations, and the 

 fertile fronds are sharply differentiated from the sterile, 

 dying soon after the spores are shed. In view of these 



