OE, THE HOME-CULTURE OF FRESH-WATER PLANTS. 



length of time, though the experiment he was pro- 

 secuting was for another and perfectly distinct 

 purpose that of ascertaining the true vegetahle 

 nature of corallines. Dr. Lankester, in his capital 

 treatise on the Aquarium, states that he kept Stickle- 

 hacks in a glass vessel with a plant of Valisneria, in 

 1849, which was, in fact, a true Aquavivarium upon 

 principles now adopted ; but he did not then an- 

 nounce it as a discovery, nor probably consider it as 

 such. Mr. H. Warrington was, in fact, the first 

 (in 1850) to publish, in a paper communicated to 

 the Chemical Society, a series of observations upon 

 the subject. In that essay he entered, with some 

 detail, into the functions assigned to plants for the 

 conversion of carbonic acid gas into oxygen, and the 

 consequent necessity of their presence for the pre- 

 servation of animal life, which would otherwise, by 

 the quantity of carbonic acid which it throws off, 

 become poisoned by its own secretions. He further 

 stated clearly that a third, or cleansing agency, 

 was absolutely necessary, inasmuch as certain por- 

 tions of plants, or the whole, having arrived at ex- 

 treme maturity, naturally perished, and that the de- 

 caying matter so produced was calculated to cause 

 as much injury as the superabundance of carbonic 

 acid, or the absence of oxygen. In fact, parts of 



