223 PALMS BARK OF ENDOGENS. [BOOK i. 



6. The spot where the upper extremity of the woody 

 bundle enters the leaf, is either on the same side of the 

 stem by which it passes downwards, or on the side exactly 

 opposite. In this second case the woody bundle passes quite 

 through the stem. 



7. The woody bundles necessarily decussate; some in the 

 central part of the stem, others by bending suddenly to 

 enter a leaf on the side where they originate. 



8. Growth is effected in a solid organic mass, between the 

 formation of the elementary organs, and the manner in which 

 leaves are arranged. It is especially their position and the 

 succession of the systems of phyllotaxis (which generally 

 increase by specific complications in each species of Palm), 

 that we must regard as the conditions of the modifications 

 in the decurrence of the fibres and the formation of the 

 wood. 



9. The oldest part of the woody bundles is not at either 

 their upper or lower extremity; they are most completely 

 developed in the middle of their downward growth. At the 

 lower end they consist only of parenchymatous cells; at their 

 upper extremity they are divided into several finer vessels 

 which enter the leaves. 



10. The lower extremity does not extend to the roots; it 

 does not go beyond the column, where the organic separation 

 of the descending and ascending axis occurs. 



11. The stem becomes more woody and harder by the 

 growth of the ascending and decussating woody bundles; the 

 parenchym between the woody bundles also becomes thicker 

 and harder. This hardening bears a direct relation to the 

 age of the tree ; and as the elements of organisation which 

 are first formed are collected at the circumference, the stem 

 is necessarily harder in that part. (Comptes rendus, 1845, 

 April 7.) 



Endogens have no bark. They have a cortical integument 

 composed of an epiphlceum and an inner layer, analogous, 

 perhaps, to liber ; and the woody part of which, according 

 to Mohl, is formed in Palms by the introduction of the ends 

 of the woody arcs of the stem. In Tamus elephantipes the 

 epiphloeum acquires the nature of cork, but splits into 



