HORSETAILS. 137 



XII. HORSETAILS. EQUISETINE^. 



MATERIAL REQUIRED. 



Common horsetail, Equisetum arvense, L. The fertile fronds must be 

 gathered in the spring when the spores are mature. These are 

 preferably examined fresh, but may be preserved in alcohol. 

 Sterile fronds in the early stages of development may be gathered 

 at the same time, but fully formed ones will have to be obtained 

 later in the season, unless they are pressed or put up in alcohol 

 the preceding year. Underground stems, with fronds attached, 

 should be collected. 



Other species of the same genus, such as the scouring-rush, Equisetum 

 hiemale, L., and others. 



COMMON HORSETAIL. Equisetum arvense, L. 

 General Characters. 



I. Note first the habits of the plant, the places in which 

 it grows best, and the time of year when it appears above 

 ground. 



II. Compare the two forms that arise from the same 

 rootstock, the fertile and sterile fronds, noting points of 

 likeness and difference. 



III. Examine the underground stem, observing its 

 peculiarities of form, size, and structure as compared with 

 the aerial stems. 



Fertile Frond. 



I. Examine the fertile frond throughout, and describe 

 in detail its characteristic features. Notice 



