TEE FLOBAL WORLD AND GARDEN GUIDE. 239 



beautifuJ varieties, some of which are hardj, others adapted to the 

 temperature of the greenhouse. But of those that require the 

 warmth of a stove I would particularize Nymphea cerulea, on 

 account of the quantity of lovely sky-blue flowers it is ever pro- 

 ducing in succession during the season of flowering. I could 

 enumerate many otliers of equal claims in regard to their attractive 

 qualities, but my object at present is not to give a list, but to remind 

 the lovers of fine plants of these interesting subjects. But I must 

 not omit to speak of Pontederia azurea, commonly called crassipes ; 

 and of this I shall give the treatment, as practised by myself very 

 successfully, both in obtaining bloom and growth. 



Having procured two strong healthy plants, I then filled a large 

 stoneware pot with clean watex', not putting in any kind of com- 

 post, but simply the water. This was then plunged in the bed of a 

 Macphail pit, in which melons had previously been grown in July. 

 The temperature was maintained by the use of hot manure linings. 

 Whenever the plants emitted side-shoots, they were carefully pinched 

 ofi", so that the vigour should be wholly concentrated in the parent 

 plant. By this course of treatment I had the satisfaction of beholding 

 beautiful clustered spikes of flowers several times in the months of 

 September and October. The flowers were very like in colour to a 

 neglected plant called Iris chinensis. Tou may wish to learn the 

 reason which induced me to have recourse to the above treatment. 

 In the course of my visits to various gardens, I had noticed that 

 many of the cisterns in which aquatic plants were grown were so 

 fixed that the water contained in them depended for warmth entirely 

 on the heated air of the house, and not from any arrangements by 

 which the house was heated, and then a quantity of soil was gene- 

 rally deposited at the bottom of the cistern for the plants to grow 

 in. The consequence was, in many instances, it was little better 

 than a pool of stagnated water, owing in some measure to decayed 

 roots and other filth that would get intermixed with the soil, and 

 often causing a green slimy matter to accumulate on its surface. 

 Not only in private, but in public gardens have I observed this state 

 of culture — evidence enough that they were not acquainted with the 

 requirements of the plants, or else they were indifferent to their 

 value. On reflection I came to the conclusion that soil was not 

 needed for producing a healthy growth in so confined a space, and 

 that it created impurities in the water, and promoted a sickly instead 

 of a vigorous habit in the plants ; and further, that we had some 

 need to study more particularly their geographical position, because 

 numbers of our aquatics grow in very still, clear water, others where 

 the stream is constantly rushing onwards. The consideration of such 

 influences on their cultivation has induced some of our horticultural 

 establishments of late years to resort to a contrivance for imitating 

 to some extent the operations which surround the plants in their 

 native element. Then we should not be unmindful that the water in 

 which the plants are grown requires to be kept at the temperature 

 to which they would be subject in their natural locality. We all 

 know from experience how beneficial bottom-heat is to the greater 

 number of the exotics cultivated in our stoves or forcing houses. 



