FRESHWATER WEEDS. 183 



tiny grains, every grain a plant, and spreads over large 

 surfaces, so that it used to be taken for a shower of 

 bloody snow, and regarded as a phenomenon big with 

 terror. The great speed of its reproduction was one 

 cause of the marvel attending its appearance. Each 

 grain contains numerous other grains ; and, bursting, 

 produces a large number of plants ; which, in their turn, 

 throw forth a crowd of offspring in an incredibly short 

 period ; thus in some few generations, each grain has 

 literally become the ' ; mother of millions." Snow seems 

 to favour the increase of this Alga ; and if a few plants 

 have lain on the surface before the snow- nurse arrived, 

 we can easily imagine how rapidly the minute grains 

 mioiit minole with the light crvstals, and oive their own 

 brilliant colouring to the mass. Sir John Boss describe- 

 the striking appearance produced by this snow-plant in 

 Baffin's Bay, where he saw it covering miles in extent. 

 and often penetrating to the depth of ten or twelve 

 feet. 



The succeeding group, the Diatomacae, are microscopic- 

 plants, with flinty coats ; they are to the vegetable 

 creation what zoophytes are to the animal ; each weed 

 consists of a group of cells, every cell a perfect plant, of 

 a geometrical shape, but joined to its neighbour by one 

 corner ; independent, yet sharing the sap of the other 

 subjects in its little kingdom. 



A large family of plants still remain unplaced, because 

 their position is hardly yet pronounced upon by the law- 

 givers of botany. These are the Charas. By right of 

 their brick red male organs, situated singly on the stem, 



