42 NUTRITION. 



is generally upright, strong, simple, regularly 

 cylindrical, and crowned at its summit with 

 a bunch of leaves : transversely divided, it ap- 

 pears to be composed of scattered fibres, mixed 

 with cellular tissue, which unites them together. 

 At a glance it is obvious that the fibres of the 

 circumference are more close, of a firmer consist- 

 ence, and older than the inner ones, which are 

 distant, soft, and surrounded by a loose cellular 

 tissue. Each fibre consists of a bundle of tracheae, 

 and rayed and dotted vessels. The difference in 

 consistence between the circumference and the 

 centre of the trunk is always perceptible, some- 

 times very remarkable : for instance, there are 

 some palms whose exterior is so hard that a 

 hatchet can make no impression on it, while the 

 inside is a loose spongy tissue, quickly decaying 

 in a humid air. The circumference of the palms 

 corresponds to the wood of our trees, while the 

 centre is a species of alburnum. It is from this 

 central alburnum that the leaves and flowers 

 spring, or in a word, it is from the centre that the 

 development of all the parts takes place. Im- 

 mediately on the appearance of the plant a first 

 row of leaves is put forth, attached to the crown 

 by a layer of fibres the next year a second row 

 is produced within the former, and distends them 



