SERIES II. 



FLOWERLESS OR CRYPTOGAMOUS PLANTS: 



THOSE which fructify without true flowers, that is, with- 

 out stamens and pistils, and produce spores (simple cells) in 

 place of seeds. 



CLASS III. ACROGENS ; the highest class of Flower- 

 less Plants, those with a distinct axis, or stern, growing 

 from the apex, containing woody matter and ducts, and 

 bearing leaves, or something answering to leaves. 



The account of the three following families is contributed by PROFESSOR 

 DANIEL C. EATOX, of Yale College. Figures of the indigenous genera are 

 given in the Manual. 



131. EQUISETACE^S, HORSE-TAIL FAMILY. 



Perennial flowerless plants, rising from creeping rootstocks ; the 

 stems mostly hollow, furrowed, rnany-jointed, with mere scales at 

 the joints united into a sheath in place of leaves; either simple or 

 with branches in whorls about the joints; fructification in terminal 

 cone-like spikes, composed of o-antjled short-stalked and shield- 

 shaped scales, each bearing on the under surface about 6 one-celled 

 spore-cases. Contains but one genus. 



1. EQUISETTJM, HORSK-TAIL, SCOURING-RUSH. (Name from 

 the Latin, meaning horxe-t<iil.) Stems grooved, the cuticle often containing 

 silex ; each joint closed at the lower end, and bearing at the upper a tubular 

 sheath (a whorl of united leaves) which encloses the base of the next joint, 

 and is sp it into a -5 many narrow teeth as there are ridges in the stem. Seeds 

 fthat is, spores) minute, each with four club-shaped threads, which are coiled 

 a'tout the spore when moist, but uncoil suddenly when dried. Of 25 species, 

 most of them widely distributed throughout the world, four or five are com- 

 mon with us. 



1. Stems living through the winter, unbranched, or with very few branches, fruit- 

 ing in summer. 



E. hyemale, DUTCH RUSHES, SCOURING-RUSH. Common on wet banks, 

 N. : stems solitary or 2-4 together, cylindrical, l-4 high, with many rough 

 ridges ; sheaths marked with one or two black rings, and divided into 15-25 

 narrow teeth, their points deciduous. 



E. scirpoides. Wooded hillsides, from Penn. N. : stems in dense clus- 

 ters, 3' - 6' hiirh, not hollowed, very slender and wiry, entangled, about 6-fur- 

 rowed ; sheaths 3-toothed. 



