THE HORSETAILS. -15 



to a foot or more high, but less than a quarter of an 

 inch in diameter The earliest stems are to be found in 

 dry sandy places ; those growing in wet or clay soils 

 develop much later. 



The full-grown fertile stems are most attractive objects, 

 the yellowish sheaths with long, pointed, dark-brown teeth 

 contrasting very prettily with the deep flesh-colour of 

 the internodes. There are usually from six to ten of 

 these sheaths on a stem, each nearly an inch in length 

 and half an inch wide at the top, flaring upward like a 

 funnel. The upper sheaths are usually largest. In the 

 bud, the bases of these sheaths are deep yellow in colour. 



The mature cones are yellowish-brown and frequently 

 two inches in length. They are a third of an inch in 

 diameter and much like those of the scouring-rush in 

 appearance, except that they are softer and more catkin- 

 like and lack the hard terminal point. The sporophylls, 

 owing to the way they are placed in the cone, are usually 

 six-sided, but there are often more than six sporangia, 

 and the outer ends of these are plainly indicated by 

 elevations on the outer surface of the sporophylls. The 

 spores are produced in great abundance, and at the 

 proper time the slightest jar will suffice to shake them 

 out in grey-green clouds. By striking a ripe cone upon 

 the back of the hand one may shake out a little heap of 

 spores that under a simple lens may be seen suddenly to 

 boil up, at the same time becoming lighter in colour. 

 This is due to the uncoiling of the elaters as the mois- 

 ture in them evaporates and the spores prepare to drift 

 away on the wind. 



Soon after the spores have been shed, the fertile stems 

 wither and disappear. At the same time the sterile 

 fi'onds begin to be noticed, springing from the small 



