Series IL CRYPTOGAMOUS or FLOWERLESS PLANTS. 



Plants never bearing true Aowers, that is, having no stamens nor pistils, and pro- 

 ducing instead of seeds minute homogeneous bodies, called spores, in which there is 

 nothing of tlie nature of an embryo. 



Class III. ACROGENOUS PLANTS or ACROGENS. 



Cryptogamous phmts with a distinct axis or stem, growing from tho apex, and 

 with usually no subsequent increase in diameter, and furnished for the most part 

 with distinct leaves ; reproduction by means of antheridia and archegonia, sometimes 

 also by gemmation. 



Subclass I. VASCULAR ACROGENS. (By Prof. Daniel C. Eaton.) 



Stems containing both woody and vascular tissue. Antheridia or archegonia, or 

 both, formed on a prothallus which is developed from the spore on germination, 

 and upon which the conspicuous but non-sexual plant is produced. 



Division I. ISOSPOEOUS VASCULAR ACKOGENS. 



Plant producing but one kind of spore ; antheridia and archegonia both produced 

 on a prothallus. 



Order CXX. EQUISETACEJS. 



Eush-like, often branching plants, with jointed and almost always hollow stems 

 rising from subterranean rootstocks, the sterile leaves represented by a toothed 

 sheath at the joints, and the fertile ones forming a short spike at the end of the 

 stem or branches. 



There is but one genus. 



1. EQUISETUM, Linn. Horse-Taiu ScooRiKo-Rirsii. 



Perennial plants with extensively creeping rootstocks. Stems simple or branched, 

 furrowed longitudinally and many-jointed, provided with a central cavity, as well 

 as with cavities opposite the furrows and an intermediate series of minute hollows 

 opposite the ridges. The joints have closed ends, and are crowned with a toothed 



