OARPOPHTTA. 



205 



378. The spore-fruit of the Stoneworts contains, thus, 

 but one spore. This in germination sends out a jointed 

 filament, which eventually gives rise to a branching plant 

 again (Fig. 119). 



379. About 150 species of Stoneworts are known, all 

 included in the single order (20) Chaeacb^. There are 



Fig. 120.— Sexual organsofaStonewort(Cliarafragilis). a, an antherid ; 

 «, spore-fruit ; c, its crown of five cells ; b, fragment of the leaf which 

 bears the sexual organs ; p, bracteoles. Magnified about 33 times. 



two families, Nitellem and Gliarece, separated by the crown, 

 which is ten-celled in the former, and five-celled in the 

 latter. The principal genus of the first family is Nitella, 

 and of the second Ohara; each contains a dozen or more 

 widely distributed species in this country. 



Practical Studies. — {a) Search the sandy margins of ponds, lakes, 

 and slow streams for Stoneworts. They are generally found in water 

 from a few centimetres to one or two metres in depth. Preserve 

 such specimens temporarily in water which is frequently changed, 

 but for future use preserve in alcohol. 



(b) Mount carefully a considerable portion of a plant, and examine 

 its structure under a low power. Note that in some species the stem 

 (and leaves) is composed of a row of large cells surrounded by a coat 



