82 M. du Petit Thouars' Theory of Vegetable Physiology. 



Journal with a continuation of the subject, I will at future 

 opportunities arrange under their respective heads the principal 

 facts and arguments upon which the theory is supported. 



I am, gentlemen, yours truly, 



Turnham Green, July 26, 1824. John LlNDLEY. 



1. The bud is the first visible moveable point of vegetation. 

 One exists at the axilla of every leaf. 



It is manifest in the greater number of dicotyledonous plants 

 and of grasses. 



It is latent in monocotyledonous plants, in which it exists only 

 as a vital point. 



The leaf therefore is to the bud what the flower is to the 

 fruit and seed. 



2. The bud is.at first supported by the juices contained in 

 the utricles of the interior vegetable substance or parenchyma. 

 This is the operation by which the parenchyma is reduced to 

 the state of pith. 



That part is therefore analogous to the cotyledon of the 



SEED Or SEMINAL EMBRYO. 



3. As soon as the bud is formed, it is subject to two general 

 movements. 



The one is a motion upwards, or an aerial motion ; 

 The other is a motion downwards, or a terrestrial motion. 

 From the first proceed the embryos of leaves, 

 Analogous to which is the plumule ; 



From the second proceeds the formation of the new fibres 

 of the wood or bark, 



Analogous to which is the radicle. 



4. Each of these fibres is formed at the expense of the 

 cambium, or of the sap produced by the first fibres and de- 

 posited between the wood and bark. 



The fibres carry downwards the matter necessary for their 

 own elongation, 



Which matter is the descending sap. 



5. The development of the bud consists in the aerial or 

 leafy elongation of these fibres ; 



Each of which, attracted by the leafy extremity, carries up- 

 wards with it the matter necessary for its own elongation, 

 Which matter is the ascending sap. 



6. From this sap are formed two general substances, the 

 woody and the parenchymatous. (Which were long ago re- 

 cognised by Grew.) 



The woody is disposed in fibres which undergo no change. 



The 



