50 



grafted on the trunk ; neither has it the zone of vessels so 

 constant in the vegetable pith. In a transverse seciion of 

 a recently formed part, the pith is found to be composed of 

 irregularly sized cells quincuncially arranged ; and in a longi- 

 tudinal one, of cells very similar to those described as bein^ 

 found in tbe membrane of the crust, but smaller and whiter. 

 It diminishes in size with age ; in the youngest branches it is 

 nearly twice as large as in the trunk ; and near the root it is 

 entirely absent; in an examination by the microscope, the 

 newer portions are very apparently cellular, while the older 

 parts, though of the same structure, appear as if destitute of 

 the cells, from their being so closely pressed together by the 

 surrounding horny texture. 



The pith is the first part developed in the formation of 

 new branches. The branches are formed irregularly on all 

 parts of the axis, on the old as well the new portions, though 

 most abundantly on the new. The mode in which the forma- 

 tion goes on, is best observed in a longitudinal seciion. This 

 curious and important point I have examined in a great variety 

 of specimens, old and young, in sections of all parts and at all 

 seasons of the year. The lirst appearance of a branch is the 

 formation of a white speck of medullary matter, similar in 

 texture and appearance to the pith, and separated from the 

 pith of the trunk by a itw layers of horny fibre. At first, this 

 spot is very small, but it soon enlarges and becomes trian- 

 gular, having its base towards the centre and its apex towards 

 the surface; it increases in size, and that portion of the axis 

 that lies between the apex and surface becomes less till the 

 point reaches the investing membrane; this is prolonged before 

 it into a pointed prominence and constitutes the first outward 

 mark of a branch. How the first point is formed I have been 

 unable to determine, but it is evidently the result of an action 

 going on in the axis itself; and has not the least connection 

 with any of the accidental patches supposed by Ellis to be 

 portions of the fleshy crust. In proof of this it may be 

 observed, that in the longitudinal sections of seventeen spe- 

 cimens the bases of the pith of all the branches were situated 

 at about the same distance from the pith of the trunk, and 

 the pith of all observed in the process of formation, was 

 similarly situated. Whether new branches were forming in 

 the old or new parts, they all began alike and passed through 

 the same process ; so that their formation is the result of an 

 action going on in the axis, rather than of accident. 



In the Gorgoniadae which grow near the shores and off head- 

 lands, which beeome so much more bushy than those from 

 deeper water, the branches, which are long and cross each 

 other, become united at their points of crossing ; and in some 

 instances for half an inch in extent. On examination, tun 



