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XXVII. Explanation of the Cuticle of Leaves. By 

 , Mrs. A. Ibbetson. 



To Mr. TiUoch. 



T 



SiH, — L HAVE offen promised to give a tliOrouL,^h ex})lanatIon 

 of the cuticle of leaves, one of the most iiuportant subjects of 

 phytology. as being the means nature employs not only to help 

 to nourish the plant, but to bestow on it all those juices and 

 gases the various compounds it has to form, must require: the 

 cjuantities of dissections necessary to enable me to understand 

 such a subject thoroughly, have hitherto prevented my arranging 

 them properly ; but having now dedicated many months to the 

 labour, abstruse as it is, I flatter myself I am prepared to give 

 it, with all its -variations, in the two following letters. 



It is now apparent that much of the nourishment of ])lants 

 is administered by their leaves, and proceeds from tlie atmo- 

 spiiere : tiiat it is not water alone that is thus bestowed, but every 

 different mixture that produces that inexhaustible variety of 

 scents iindj/iices with which the leaves and flowers are endowed 

 for the general benefit of man and i^iimals. It becomes there- 

 fore of the greatest consequence to understand the manner of 

 receiving the dews, and to point out the mechanism of each dif- 

 ferent cuticle, how it is formed and acts in this respect to be 

 capable of retaining each sej)arate juice, nor mix them together 

 till natme by their conjunction is ready to produce the new 

 compound. I have in a former letter shomi rhiit no moisture 

 enters the leaves but through the hairs, or some projection pro- 

 truded in the cuticle ; but the art with which the upper skin is 

 formed in points and bags to draw in the moisture, and the various 

 contrivances to secure the gases, are so tvovderful, that it will 

 scarcely be credited by those not used to contemplate and ad- 

 mire tlie astonishing works of the Almighty, in tracing the 

 many species of leaves, I find their cutfcles vary according to 

 the quantity of nourishment they receive and dispense to the 

 plant; and it is also remarkable, that the pabulum of the leave* 

 lessens in substance in exact j^roportion to the quantity of liquid 

 absorbed from the atmosphere : the more hard and.' solid the 

 pabulum, the less is the quantum of nourishment received from 

 the dews. 



In describing the formation of leaves, I think I proved that they 

 l)roceeded entirely from the exterior of the plant, and had little 

 or no connexion with the interior parts. This is so apparent, 

 that a plant entirely dead within, has been known to throw out 

 its leaves the ensuing spring. Having long before formed the 

 leaf-bud, it has still the power to act: the line of life not reach- 

 Vol.44. No. I97.&/J/. 1814. L ing 



