128. Plants floating on the water. Leaves opposite, or else alternate 



and imbricate, without breathing pores. SALVINIACE^. 

 Growing in wet places, with creeping, thread-like stems. Petioles 

 long. Leaves neither imbricated nor opposite, either having no 

 blade, or consisting each of four heart-shaped leaflets, furnished 

 with breathing pores. MARSILIACE^. 



FILICES OR FERNS. 



In studying the ferns the spore cases must be examined with the 

 microscope to determine the presence and extent or the absence 

 of a jointed, elastic ring. 



Indusium, the membranous awning over a cluster of spore cases. 



Sori, patches of fruit, forming dots or lines on the under surface 

 or margin of the leaves. 



129. Spore cases furnished with a nearly or quite complete elastic 

 ring. Frond circinate or unrolling endwise from the base. 130 

 Spore cases with a very short ring or none. 



Fronds straight, never circinate. Clusters of spore cases forming 

 simple or pinnate spikes distinct from the leafy part of the frond 

 which is lower down on the stem. Spore cases opening down the 

 side. OPHIOGLOSSACE.E. p. 563. 



Fronds unrolling endwise from the buck 



Natives of tropical regions. Sori on the back of the green frond. 



Spore cases commonly joining together, opening by a pore, or a 



slit down the side. MAKATTIACE.E. 

 Natives of temperate regions. Sporanges often occupying entire 



fronds or pinnae, so that the fertile fronds or pinnae are unlike 



the green leaves. Spore cases opening across the apex. 



OSMUNDACE^E. p. 362. 



130. Ring covering the spore case like a lid or cap. Spore case 

 opening down the side. ScHiz-aEACE^:. p. 362. 



Ring vertical, extending from the base quite around the case which, 

 when ripe, opens in a plane parallel with the base. Sori on the 

 back or margin of the frond. POLYPODIACE^E. p. 360. 



Ring transverse or parallel with the base of the spore case, or 

 slightly oblique. 



