London Horticultural Society and Garden. 623 



are carefully guarded from any kind of injury. Mr. Lindley urged growers 

 of bulbs to try to multiply them in England ; and, to encourage them, men- 

 tioned the fact, that Mr. Knight had contrived to make the Guernsey 

 lily flower luxuriantly with him for several successive years, though 

 that plant generally deteriorated in this country as much as the hyacinth. 

 Cape bulbs are particularly difficult to manage in this country, from the 

 difficulty of keeping their leaves in health. Succulent plants will not bear 

 moisture, from their want of evaporating pores. 



It is very difficult to make plants grow in rooms. They must necessarily 

 be deficient in the three important auxiliaries to vegetable life, light, air, 

 and moisture ; the latter of which cannot be maintained in apartments 

 that are daily occupied. In large towns, plants cannot thrive even 

 in the open air, as the minute particles of soot, which are constantly float- 

 ing about, settle upon their leaves, and choke up their pores. The gases 

 produced by the combustion of coal, &c, are also injurious to plants. 

 Sulphurous acid, which abounds in the atmosphere of London, turns 

 the leaves yellow ; and the want of evaporation and absorption by the 

 leaves prevents the proper elaboration of the sap, and makes the trees 

 stunted and unproductive. 



Green-houses and hot-houses require great care in their management ; 

 but it is not easy to lay down rules for that purpose. The principal 

 object is, of course, to imitate the native climates of the plants kept in 

 them ; and to do this effectually, by artificial means, requires not only 

 science, but practice. The first point to be ascertained is, the kind of 

 climate natural to the plant ; and, to do this, it is not merely necessary to 

 know the longitude and latitude of the place where it grew. Many cir- 

 cumstances combine to produce a variation in climate. Islands are gene- 

 rally warmer than continents ; and the vicinity of mountains, or rivers, 

 or being in an exposed or sheltered situation, will often occasion most 

 remarkable differences. Climate always varies according to the elevation 

 of any given spot above the level of the sea; 200 yards of vertical 

 elevation being considered equivalent to a degree of latitude. Isothermal 

 lines drawn across one of Mercator's charts, according to the degrees of 

 latitude, and marked with the plants flourishing in different countries, 

 would show strongly this fact. Whatever warmth may be given, or care 

 bestowed, no plants will grow well without change of ah' and abundance 

 of light. For this reason, peaches seldom, if ever, thrive below vines ; as, 

 even if they are so contrived as to be placed at the back of the house, 

 while the grapes hang in front, the stone pavement of the path prevents 

 the air from getting to their roots. 



Pits are small hot-houses ; and there appears no sufficient reason why 

 they should not be managed exactly in the same manner. The professor 

 observed, however, that gardeners generally appear to think otherwise ; as 

 they are in the habit of giving their pits a lining of dung, &c, to produce 

 what they call bottom heat, which they never think of applying to hot- 

 houses. This practice the professor strongly reprobated. He maintained 

 that there is no such thing as bottom heat in nature; and that it is con- 

 trary to all established theories, to produce excessive heat and ferment- 

 ation round the roots of cucumbers, and such plants as are generally grown 

 in hot-beds. As a proof that this practice is not a good imitation of nature, 

 he mentioned that the best melons in Persia are grown on ridges of earth 

 having water in the channels between them. 



In conclusion, the professor apologised for having only imperfectly 

 developed his subject. He had found it impossible, he said, to compress 

 into six lectures what might have afforded ample material for fifty ; and 

 he threw himself upon the consideration of his auditors, to excuse any 

 omissions or errors which he might have made. 



