EQUISETACKJ1. 



181 



Fig. 273. 



2. B. lunarioi'des, Swartz, is occasionally found. It is 

 easily distinguished from No. 1 by the sterile portion of the 

 frond being long-petioled instead of sessile. 



17. OPHIOGL-OS'SUM, L. ADDER'S TONGUE. 

 0. VUlga'tum, L. Sterile part of the frond 

 ovate or elliptical-oblong, 2-3 inches long, 

 rather fleshy, sessile, near the middle of the 

 stalk; the latter 6-12 inches high. Bogs 

 and grassy meadows. 



ORDER CYIII. EQTJISETA'CEJE. 

 (HORSETAIL FAMILY. ) 



The only genus of the Order is 

 EQ,UISE'TUM,L. HORSETAIL. SCOURING EUSH 

 Fig. 272 is a view of the fertile stem 

 of Equise'tmn. arvense, the COMMON- 

 HORSETAIL, of about the natural size. 

 It may be observed early in spring 

 almost anywhere in moist sandy or 

 gravelly soil. It is of a pale brown 

 colour, and in place of leaves there is 

 at each joint a sheath split into sev- 

 eral teeth. At the summit of the stein 

 is a sort of conical catkin, made up of 

 a large number of six-sided bodies, each attached to 

 the stem by a short pedicel. Each of these six- 

 sided bodies turns out on examination to be made 

 up of six or seven sporangia or spore-cases, which 

 open down their inner margins to discharge their 

 spores. Figs. 273 and 274 are enlarged outer and 

 inner views of one of them. The spores themselves 

 are of a similar nature to those of the Ferns, and 

 reproduction is carried on in the same manner; but 

 each spore of the Horsetail is furnished with four 

 minute tentacles which closely envelope it when 

 moist, and uncoil themselves when dry. The use 

 Fig. 272. of these tentacles is doubtless to assist in the 



escape and dispersion of the spores. 



Fig. 274. 



