48 
the surface of the axis dark, and polished. Ellis has 1,,a< | it 
observations similar to these on this genus 1 *, which hare i* 
been allowed to hare their due influence in the formatin' 3 
the theories of seme of our physiologists. - 
The axis is solid, horny, fibrous, flexible and formed . 
series of concentric layers. It varies iu thickness accoi* ' ’ 
to age, and is more solid in the older portions than in ^ 
branches which are of a horny membranaceous tes' 11 
Though the thickness of the axis is in accordance wnb 1 
age of the specimen, yet it depends for its existence on 
soundness of the fleshy crust. For if from accident or ^ 
incrustation of corallines, the axis be denuded, it ceases ^ 
increase, while above and below the point of denudation 
grows as usual. In a transverse section the concern , 
layers, in lighter and darker lines, are very observable, ' v 
the white central pith. This view hears a great resem > f3 > 
to a similar section of the wood of an exogenous plant, 
presents (wo remarkable deficiencies in the absence 0 J 
radiating medullary rays and cells which render the " t 
such a beautiful object for the microscope. The axis u 
the root is very compact and the circular layers conseque .y 
less distinct than higher up ; in the branches it is mer 
membranaceous. In a longitudinal secuon the coneen 
layers arc as apparent as in the transverse one an ^ 
very closely' resembles a similar section in wood. . j S 
fibrous and rends very freely. In different parts ot ,y 
section white spots of a cellular substance are freq« c . 
observed irregularly distributed between the horny U.V ^ 
This is most frequently observed about the root m {0 
axilhe of branches, especially where two arise close a 
each other. In such a case I have frequently seen sev ^ 
successive layers of it with a few of the horny n lire 
tween, and in a case now before me there are b'e e 
distinctly marked. The while substance, mentioned ,y 
as being found in the la: ge cavities of the branches, so c 
resembles these white spots in colour and texture as to 1 
to a common origin for their production : a secretion or ^ 
mation from the investing membrane. This appears to o . gt 
substance, supposed by Ellis to be the remains ot a pc ^ 
of the fleshy crust which had been enclosed betwee 0 I 
liorny layers. He says, “ we frequently meet with i* 
calcareous matter enclosed between the circles, wbi j), 
evidently nothing else but the decayed flesh ol the an „ 
which has been covered and enclosed by the subseq 
growth of the same animal.” This however, 1 believe 0 e> 
the true explanation ; in the case of the globular excres^^. 
Ellis and Solander’s Zooph., p. 60. 
