602 APPENDIX 



quite near the foot or at a distance of some centimetres awa\ from it. The primary 

 branches may bear secondary branches, and these, again, produce lateral offshoots, and so 

 on. These lateral branches, like the main stem, do not follow a straight course, but twist 

 and turn about in a more or less irregular manner; they also terminate in irregularly 

 blunted points. The branching follows no fixed law, but the branches spread as much as 

 possible, and never arise two at the same level on the parent stem. 



The angle at which the branches are inclined to the parent stems varies considerably. 

 It is often between 40° and 50°, but may be obtu.se, so that the. branch is directed back- 

 wards, or, on the other hand, so acute that it runs close beside the parent stem and may 

 actually fuse with it, only to separate again after a short distance. Such an intergrowth 

 may take place also between branches of the same colony which have originated at different 

 spots, or between branches of neighbouring but independent colonies. 



Though two branches never originate at exactly the same level on the parent stem, 

 the difference in level between them amounts, as a rule, to only a few millimetres, though it 

 may be several centimetres. The branches are usually crowded together at the attached 

 end of the parent stem, and are less numerous towards the free end. At the point where- 

 a branch originates, the pnrent stem is somewhat flattened, so that its outline in section is 

 oval instead of circular. The same flattening may be obser\cd also in other jjarts of the 

 stem where there is no obvious reason for it. This is often considered to be due to some 

 temporary disturbance in the economy of the colony. 



The general form of a coral-stock, the system according to which it branches, and the 

 actual direction of the branches vary according to the locality in which it grows, its depth 

 beneath the surface of the sea, and so on. Colonies ^\•hich have grown under similar 

 conditions usually resemble each other in form, so that we may reasonably conclude that 

 the form taken by a colony depends upon the conditions under which it grows. So 

 characteristic is the form of coral-stocks from different districts of the Mediterranean that 

 an expert confronted with a collection of corals from the same locality has no difficulty in 

 naming at once the place from whence they came. Corals from the Algerian and Tunisian 

 coasts, from Sicily, and especially from Sciacca, from Spain, and from Provence, show 

 remarkable differences in this respect, differences which are important, inasmuch as they 

 render the coral more or less suitable for certain purposes, and therefore more or less 

 valuable. 



The furrowed surface of precious coral is another of its characteristic features. These 

 fine furrows run in a direction either parallel to the length of the stem and its branches or 

 in more or less of a spiral. When a furrow reaches the point of origin of a branch, it 

 either passes to one side of it or divides into furrows, which enclose the spot, and which 

 frequently unite again after a short course. These furrows are always more numerous- 

 towards the base of the stem, since a certain proportion disappear in their course from the 

 base towards the apex. The distance between adjacent furrows is always small, never less 

 than ^ millimetre and never more than 1 millimetre. 



Another equally striking feature of a piece of natural coral is the presence of small,, 

 circular, shallow depressions, measuring at most two millimetres in diameter. They may 

 lie so close that their edges touch, or, on the other hand, they may be separated by a space 

 of a centimetre. They mark the spots where grew the individual polyps of the colony of 

 which the piece of coral was the axis. 



These characteristic ridges and depressions are an invariable feature of the natural: 

 surface of precious coral. When absent, it is quite certain that they have been removed by 

 polishing or by some other artificial process. Besides the depressions in the surface of coral. 



