CliXPTOGAMOUS OK FLOWKKLESS PLANTS. 0:17 



and deflt'xed; fruit-dots 10-13 on a piiiiui. Fronds G'-IS' 

 high, 1-3' wide; s!:ipc very short. 



** Frondu 2-3-pifinaie or pinnatifid. 



A. MOXTAXUM, Willd. Fronds small, ovate-hmceolate, 

 pinnate; pinnxB iyi\'^, petioled, ovate or trianguhir; tlie 

 lower ones pinnatifid ; the upper ones incised ; divisions 

 toothed or serrate ; fruit-dots very short, the basal ones 

 often with a double indusiuni. Mountains, Xorth and 

 West Texas. Fronds 2-5' high, with a winged greenish 

 rachis, and a stipe nearly as long as the frond. 



WATER-FERNS. Order, Hydropterides. 



Aquatic herhs, witli the sporangia of two forms, borue at 

 the base of the leaves and bursting irregularly. 



ISOETES, L. 



Plants comp)Osed of fibrous roots and filiform cellular 

 leaves, IV ithout any apparent stem; sporangia sunk in an 

 excavation of the dilated base of the leaves, plano-convex, 

 membranaceous, filled with transverse threads and minute 

 powdery spores; those of the central leaves filled with 

 larger spores. 



I. FLACCIDA, Shuttlw. Immersed; leaves very long 

 (l-J°-2''), slender, flaccid, yellowish-green; sjwres very 

 small, minutely pulverulent, not reticulated. In lakes 

 and clear streams. 



AZOLLA, L. 



Minute floating 2)la7its, with pendent roots, pinnately 

 branching stems, and thick imbricated cellular leaves; 

 sporangia of two kinds, ovoid, sessile on the under side of 

 the branches, and covered with a thin membrane; the 

 smaller kind opening transversely, containing several an- 

 gular grains, attached to a central column, the larger 



