ON AQUATIC PLANTS. 897 



Only since the introduction of hot - water apphances for 

 heating horticultural buildings has the cultivation of these plants 

 been undertaken on a comprehensive scale, the most complete 

 collections having been at first formed in botanic gardens, 



where for many years they have received special attention. 

 Excepting in a limited number of instances their cultivation, 

 save in these establishments, has not been undertaken with 

 such an enterprising spirit as they merit, or as in the case 

 of plants which have a greater cornmercial value, but 



3 



