EQUI3ETACEJE. (HORSETAIL FAMILY.) 585 



SERIES II. 



CRYPTOGAMOUS OR FLOWERLESS PLANTS. 



VEGETABLES destitute of proper flowers (stamens and 

 pistils), and producing, in place of seeds, minute bodies of 

 homogeneous structure (called spores) , in which there is 

 no embryo, or plantlet anterior to germination. 



CLASS III. ACROGENS. 



Cryptogamous plants with a distinct axis (stem and 

 branches), growing from the apex only, containing woody 

 fibre and vessels (especially ducts), and usually with dis- 

 tinct foliage. 



ORDER 135. EQUISETACE^E. (HORSETAIL FAMILY.; 



Leafless plants, with rush-like hollow and jointed stems, arising from run- 

 ning rootstocks, terminated by the fructification in the form of a cone or 

 spike, which is composed of shield-shaped stalked scales bearing the spare- 

 cases underneath. Comprises solely the genus 



1. EQUISETUUI, L. HORSETAIL. SCOURING RCSH. (Tab.14.) 



Spore-cases (sporangia, tfiecce) 6 or 7, adhering to the under side of the angled 

 shield-shaped scales of the spike, 1 -celled, opening down the inner side and dis- 

 charging the numerous loose spores. To the base of each spore are attached 4 

 thread-like and club-shaped elastic filaments (elaters), which roll up closely 

 around them when moist, and uncoil when dry. Stems striate-grooved, rigid, 

 the hard cuticle abounding in silex, hollow, and also with an outer circle of 

 smaller air-cavities corresponding with the grooves ; the joints closed and solid, 

 each bearing instead of leaves a sheath, which surrounds the base of the inter- 

 node above, and is split into teeth corresponding in number and position with 

 the principal ridges of the stem : the stomata always occupying the principal 

 grooves. Branches, when present, in whorls from the base of the sheath, like 

 the stem, but without the central air-cavity. (The ancient name, from fquus, 

 horse, and seta, bristle. ) 



