78 STRUCTURAL BOTANY 



TYPE VI 



THE FIELD HORSETAIL (Equisetum arrense, L.) 



The Vascular Cryptogams at present existing in the 

 world belong to three great stocks or Classes. We have 

 already examined representatives of two of them 

 namely, a Club Moss and a Fern. It remains for us 

 now to make the acquaintance of the third Class, that of 

 the Horsetails. The latter are not now a very important 

 group, for there is only one living genus, containing 

 about twenty species. But small as the family is in 

 these days, it is a very ancient one, and has now no 

 connection whatever with its neighbours among the 

 Ferns and Club Mosses. In early geological times, 

 especially in the far-off period when the coal-beds 

 were being formed, the Horsetail family were in the 

 height of their glory, and were represented by a number 

 of very diverse forms, many of which grew into trees. 

 Hence this good old stock, though now so reduced, is 

 quite as worthy of our study as its more prosperous 

 fellows. 



Several species of Horsetail are natives of England, 

 and some are very common. In general habit they all 

 bear a strong family likeness to each other, all having 

 stiff, upright, jointed stems, with whorls of little-developed 

 leaves, those of each whorl being united to form a sheath 

 around the stem. If the stem is branched, its branches 

 are also in whorls, the whole plant having a very formal 

 and regular appearance (see Fig. 38). The fructification 

 is in the form of cones, each of which is borne at the end 

 of an upright stem, or of a branch. In some species 



