EQUISETACKiE. (HORSETAIL FAMILY.) 653 



SERIES II. 



CRYPTOGAMOUS or FLOWERLESS PLANTS. 



Vegetables destitute of proper flowers (i. e. no stam'ens 

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

 homogeneous structure (called spores'), iu 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 some 

 kind of foliage. 



Order 129. EQUISETACE.E. (Horsetail Family.) 



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

 ning roolstocks, terminated by the fructification in the form of n cone or spike, 

 ■which is composed of shield-shaped stalked scales bearing the spore-cases 

 underneath. — Comprises solely the genus 



1. EQITISETUM, L. Horsetail. Scouring Rush. (PI. 15.) 



Spore-cases (sporangia, theca) 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 numerons loose spores. To the hase of each spore are attached 4 

 thread-like and club-shaped elastic filaments, which roll up closely around the 

 spore when moist, and uncoil when dry. — Stems mostly from running root- 

 stocks, striate-groovcd (in many the hard cuticle abounding in silex), hollow, and 

 also with an outer circle of smaller air-cavities corresponding witli the grooves; 

 the joints closed and solid, each bearing instead of leaves a sheath, which sur- 

 rounds the hase of the intemode above, and is split into teeth corresponding in 

 number and position with the principal ridges of the stem : the stomata in the 

 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 cquus, 

 horse, and seta, bristle. ) 



