ON THfi HATRS of plants. «• 



Ihe rind, and an excrescence of it ; probably arising from Bfi" 

 extreme tendency in that part to grow in the same manner 

 as the quercus suber, the ulmus campestris, and many 

 others, the rind of which is a sort of cork, always increasing. 

 The 2d sort of thorn is that which in the Crataegus is a dis- 

 order in the tree, to which some plants are peculiarly sub- 

 ject: a sort of missed bud, from the stoppage of the line of 

 life,caused probably from the momentary check of the juices, 

 on some sudden alteration of the weather; as I have observ- 

 ed, that, when the barometer and thermometer are without 

 much variation, except the natural one of day and night in 

 the latter, no thorns come out. I have measured at such a 

 time a slvoot three quarters of a yard long, without a thorn. 

 But when m the spring alterations are frequent, the branches, 

 will be scarce two inches, and always ending in a long one: 

 and on dissecting this, the line of life will be found to have 

 stopped, before any other part of the plant. 



I intended to give merely a sketch of this subject, till I Hope to intro- 



better understand how to inflate the hairs with a coloured °'^/^5'*^® 



subject mote 

 liquid, and till I can more thoroughly comprehend their uses indeuil. 



and management; for this indeed I should have waited, but 

 that it was absolutely necessary to prove, that I would not 

 have written against the perspiration of plant, without a 

 complete conviction of the truth of my assertion: *' that the 

 whole system of perspiration could not be supported against 

 the absolute proof the solar microscope adduces of its false- 

 hood." Tf I were rich, I would certainly have the instru- 

 ments imitated in glass, properly magnified (if it could be 

 dene) as I think much might be learnt from it. It is the 

 mechanism of nature: we tallc much of its simplicity, but it 

 surely consists only in not making use of more contrivance 

 than is necessary; and when the mechanic powers are 

 wanted, can we do better than study them from models-so 

 perfect, forms so wonderful? and though we could not suc- 

 ceed in forming a sort of air pump in a hair; yet it might' 

 serve to teach us to simplify our machines, and to rectify 

 tpany of our mistakes. 



Your obliged servant, 

 Cowley Cottage, AGNES IBBETSON. 



July 29th, 1811. - ' v! 



