AND OTHER BULBOUS-ROOTED PLANTS. 211 



had germinated, as well as ultimately only grown, in a rich soil. The 

 water in this case occasioned the extension of the roots, and the develope- 

 ment of the leaves, and thus was instrumental in forming organs capable 

 of collecting and assimilating new matter ; but exclusive of some impu- 

 rities it contained, it probably had not given a particle of organisable 

 matter to the plant. The formation of organs, and the action of those 

 organs when formed, must not therefore be confounded, as has generally 

 been done, and constantly by chemists who have endeavoured to ascertain 

 the action of the leaves upon the surrounding air ; and hence appear to 

 have arisen the confused and contradictory results of their experiments. 



I am wholly ignorant of the mode of management by which bulbous 

 roots of different kinds, acquire so much greater perfection in the hands 

 of the Dutch gardeners, than in those of our own countrymen : but I 

 suspect that the Dutch gardeners employ subsoils of very great depth and 

 richness, with which the bulbs are prevented coming into contact by the 

 intervention of a thin layer of dry sand, with which substance they may 

 be also thinly, or only partially, covered ; and I am in part led to adopt 

 this opinion, by observing the similarity of character in the external 

 membranes of their bulbous roots, and of those of the shallots, which had 

 been wholly exposed to the sun and air. 



XXIX. ON THE APPLICATION OF MANURE IN A LIQUID FORM TO 



PLANTS IN POTS. 



[Read before the HORTICULTURAL SOCIETY, May 11th, 1814.] 



THE quantity of earth, which the most firm and solid parts of trees 

 afford by analysis, is well known to be very small ; and even the species 

 of these earths have been proved, by the younger Saussure, to be 

 dependent, to a great extent, upon the component parts of the soil, in 

 which the trees happen to have grown. A large extent and depth of 

 soil seem therefore to be no further requisite to trees than to afford them 

 a regular supply of water, and a sufficient quantity of organisable matter ; 

 and the rapid growth of plants of every kind, when their roots are con- 

 fined in a pot to a small quantity of mould, till that becomes exhausted, 

 proves sufficiently the truth of this position. 



I have shown in a former communication*, that a seedling plum-stock, 

 growing in a small pot, attained the height of nine feet seven inches, in a 



* See page 194. 



