434 ISOET^E. (QUILLWORT FAMILY.) 



SERIES !'. 



PTERIDOPHYTA (VASCULAR CRYPTOGAMS), or 

 FERNS AND THEIR ALLIES. 



PLANTS destitute of proper flowers, that is, having no sta- 

 mens and pistils, and not producing seeds. A distinct axis 

 containing fibro-vascular bundles, as does the foliage when 

 there is any. Sexual reproduction by means of antheridia 

 and archegonia, one or both of which is formed on a prothal- 

 lus which is developed from the non -sexual spore and upon 

 which the conspicuous but non-sexual plant is produced. 



CLASS I. LYCOPODINEvE. 



Plants with a solid, dichotomously branched, leafy stem, 

 the leaves imbricated and often giving to the lower forms a 

 moss-like appearance, but may be distinguished from moss 

 leaves by their midrib. Sporangia in the axils of simple 

 leaves or bracts. 



SUBCLASS I. HETEROSPOMLE. 



Producing spores of two kinds, the larger (macrospores) 

 producing a prothallus with archegonia, the smaller (micro- 

 spores) producing a prothallus (rudimentary) with sperm-cells. 

 Leaves with ligules. 



ORDER 91. ISOET^E. (QUILLWORT FAMILY.) 



Mostly aquatic plants, with a short solid conn-like stem (trunK) and 

 elongated grass-like leaves, the bases of which are expanded and have 

 thin stipule-like infolded margins (the velum), which enclose large 

 simple ovoid thin- walled sporangia; the outer ones containing large 

 spherical trivittate macrospores; those of the inner leaves filled with 

 very minute grayish triangular microspores. 



