284 Mr. Main's Rtjoifider to the Author 



cially as the results of such experiments are not always 

 uniform, differing according to the time and manner of per- 

 formance ; indeed, I might add, at the will of the performer. 

 I have already alluded to the sap and membranous frame or 

 structure of vegetables; but there is another equally im- 

 portant matter to be adverted to; I mean, the elements of 

 vegetables. These, you say, are chiefly the constituents of 

 water, viz. oxygen, hydrogen, and carbon ; the chemical 

 essences or bodies of which the vegetable frame is com- 

 pounded; the pabulum by which it is enlarged, and without 

 constant supplies of which a plant remains stunted, or would 

 in the end inevitably perish. All this 1 firmly believe, and 

 it is an admission which may appear at first sight to be cor- 

 roborative of all you have advanced, and contend for, relative 

 to the growth of plants; but I presume to think that a little 

 further consideration and explanation will show, not only that 

 such distinction is just, and therefore necessary, in physio- 

 logical investigations, but that they, viz. vegetable elements 

 and vegetable organisation, should never be confounded 

 together, so as to attribute to the former the power of 

 generating 'the latter. Your ideas appear to be, that vege- 

 table food, in conjunction with the vital energies and 

 *' chemico-electrical influences" of the earth and atmosphere, 

 goes directly to form new organs. My opinion is, that nu- 

 trition received into the system goes only to increase the 

 quantity of the elements already existing in the membranous 

 fabric, sei'ving to dilate and expand the same ; not by 

 addition of new cells, tubes, or fibres, but simply by enlarge- 

 ment of those already there. You assume that, by certain 

 and peculiar combinations of vegetable elements acted on by 

 " the great natural agents," new organic bodies may be 

 generated. I humbly imagine this to be impossible ; because 

 such a phenomenon has never been seen, nor do we ever 

 witness any vegetable body produced, unless it originates 

 fi'om a seed, propago, tuber, or other dissevered member of a 

 plant. The organisation and specific structure are certainly 

 rudimental ; these are amplified, as already observed, by the 

 elemental fluids absorbed by the receptive spongioles and 

 pores of the cuticle, but not one additional cell can possibly 

 be formed by any such augmentation of either gaseous or 

 aqueous fluids. Can we suppose, with Buffbn, that nature 

 abounds in ^Hiving organic particles ;" and that these, by 

 concurring circumstances, associate by accident, and form 

 vesicles, laminae, tissues, fibres, and all other organic struc- 

 ture, in the same way as crystals are formed ? Such doc- 

 trine, I presume, cannot be sound philosophy. If there were 



