242 PHILOSOPHICAL TRANSACTIONS. [aNNO 1758. 



of supporting itself, but is sustained by the strength of the waters, in which it 

 floats. 



The substance of the plant is not so solid as that of the common alga, which 

 is capable of drying as it fades, and of being kept; whereas the leaves of this 

 great alga shrink and wither in the air, become of a blackish colour, and ver}'^ 

 friable, or indeed soon fall into putrefaction. But what we find particular in this 

 plant is its root or foot: first, this pedicle extends in ribs, like what we call the 

 thighs of certain trees: these thighs are in right lines. They are about 3 or 4 

 lines high towards the pedicle, and, ending, are lost. They flourish and spread 

 at the bottom, forming an elliptical bladder, like an egg, flattened above and 

 below, and rounded at the sides, being entirely empty : it is rough without, and 

 very smooth within. This egg, or oval bladder, is exactly round at the ends of 

 the great diameter, but varies a little in the less diameter, and forms itself like 

 the body of a fiddle. The under part is a little flattened; and there is a hole, 

 which is very considerable, in the centre of the two diameters. This hole is 

 about an inch wide, and is quite round; it gives passage to the root, or pivot; 

 the edges appear to turn a little inward ; and it is by this hole that the egg fills 

 with sea-water. The whole substance of this bladder or egg is of a coriaceous 

 matter, firm and transparent, and of a clear green ; nor can there be any fibres, 

 either longitudinal or transverse, observed on it. 



The vault at the top, surmounted by the thighs, is as it were granulated ; but 

 at the rounding of the egg it produces a kind of mammae, or little elevations, 

 very round and cylindrical, entirely full, of the same nature and substance with 

 the egg. In examining the under part of the egg were found a 2d rank of these 

 mamellae, somewhat longer than the first, and at equal distances from each other, 

 in a circular line: then a 3d yet longer: then a 4th, which at the extremities 

 were bifurcated; and at last a 5th rank, which divided into 3, and sometimes into 

 5 branches : these last, placed round the hole, were wreathed inwards, and several 

 were joined together, and only formed a small body; and in wreathing themselves 

 thus they close and embrace the pivot mentioned below. None of these mamellae 

 have any apparent opening; their substance is compact, of the same nature with 

 the bladder or egg, that produces them. Below the trunk and thighs the plant 

 protrudes a pivot, of a like substance with that of the bladder. This pivot, 

 which is large at its origin, proceeding thus from the trunk and thighs, forms 

 something like the knot of the sea-tree: it descends perpendicularly to the trunk, 

 diminishing as it lengthens, and as it grows round; and then divides into a 

 number of mamellae, branched and wreathed inwards so firmly, as not to be 

 retracted; of a coriaceous nature, blackish, forming a bunch like what we call 

 the rose of Jericho. This bunch, or wreathed rose, incloses a heap of gravel, 

 as if petrified or hardened, and ends on a level with the hole of the egg, ex- 



