ACROGENS. 191 



CLASS III. ACROGENS. 



Substance of the plant composed of cellular tissue chiefly ; 

 spiral vessels or ducts only present in the highest orders. 

 Stem either increasing by an extension of its point, or by 

 a developement in all directions from one common point ; 

 not increasing in thickness when once formed. Sexual organs 

 absent. Reproduction taking place by spores, or by a mere 

 dissolution of the utricles of tissue. 



184. Lycopodiacea. Plants, with creeping stems, the 

 axis abounding in annular ducts. Organs of reproduction 

 axillary sessile thecse, containing either minute powdery mat- 

 ter, or.sporules, marked at the apex with three minute ridges. 



USES. Some are powerful emetics and cathartics, especially 

 L. Selago and rubrum. 



TYPICAL GENERA. Lycopodium, Bernhardia. 



185. Filicales or Filices. Leafy plants producing a rhi- 

 zoma. Leaves usually coiled up in vernation, with dichoto- 

 mous veins of equal thickness. Thecse or sporangia arising 

 from the veins upon the leaves, pedicellate with an elastic 

 ring, or sessile and destitute of a ring. 



Division 1. Polypodiacea. Thecse with a vertical, usually 

 incomplete ring ; bursting irregularly and transversely. 



Division 2. Gleicheniacea. Thecse with a transverse, oc- 

 casionally oblique ring, nearly sessile, and bursting lengthwise 

 internally. 



Division 3. Osmundacea. Thecse with an operculiform 

 ring, or without any ; reticulated, striated with rays at the 

 apex ; bursting lengthwise, and usually externally. 



Division 4. DaneEacea. Thecse sessile, without any ring, 

 concrete into multilocular sub-immersed masses, opening at 

 the apex. 



Division 5. Ophioglossaceee. Thecse single, roundish, coria- 

 ceous, opaque, without ring or cellular reticulation, half 

 2-valved. Vernation straight. 



USES. The rhizomata of some are astringent ; that of Ne- 

 phrodium Filix mas has been used as an anthelmintic. In 

 some countries the pith of the stem is used as food by the 

 natives, especially in the islands of the South Seas. 



TYPICAL GENERA. Polypodium, Pteris, Adiantum. 



