THE adder's tongue FAMILY. 



Ill 



become great favourites with amateur fern-growers. S. ser- 

 pens, a native of Jamaica, is remarkable for a peculiar habit 

 of changing its colour during the night, the whole plant be- 

 coming white, and when growing in a mass is visible at a 

 considerable distance, changing again to green on the re- 

 turn of daylight. 



The Pepper-wort Family. 



(Marsileace^.) 



Plants floating, or growing in water, rarely on land, having 

 grass or trefoil-like leaves. Their spore-cases are produced 

 either from the rhizome, or the stem, or on the footstalks of 

 the leaves. (Fig. 11, b.) This small family is composed of 

 from twenty to thirty species, the greater number being 

 natives of temperate countries of the Northern hemisphere. 

 They are found floating on the surface, or growing at the 

 bottom of pools and lakes. Several species of Isoetes are 

 found on land. They are of no economic use except Mar- 

 silea macropus, which occupies large tracts of flooded land in 

 the interior of Australia. When dried up the spore- cases, 

 which are about the size of wheat-grains, are found in large 

 quantities and used as food by the natives. It came into 

 notice some years ago, in the ill-fated Burke and Wills 

 expedition, under the name of Nardoo. 



M. quadrifolia is a native of some parts of Europe, but in 

 this country the family is represented hj Pilularia glohulifera 

 and Isoetes lacustris, two plants with grass-like leaves, grow- 

 ing at the bottom of shallow pools and lakes. 



The Adder's Tongue Family. 



(Ophioglossaceje.) 



Plants with leafy erect or pendulous fronds growing on 

 the earth or on trees. The spores are contained in valved 

 cases (Fig. 11, c), forming simple or branched spikes, rising 

 from the surface of the frond. In this country the family 

 is represented by the common Adder's tongue {Ophioglossum 



