16 TRANSACTIONS OF THE [oCT. 13, 



six inches above the ground, were small vertical shoots about 

 three or four inches apart and looking very much like the teeth 

 of a very long wooden rake. These shoots, I afterward found, 

 come from the long, sucker-like roots of the Avicennia and also 

 of the Buttonwood {Conocarpus cj'ectus). Later, on the west 

 side of Andros, I found these plants growing near the water and 

 also higher up on the beach, which here was a very fine calcare- 

 ous deposit. This deposit had been slightly raised by the growth 

 of the shoots, and higher up on the shore, where in contact 

 with the shoots, it had hardened into rock. This, I believe, ex- 

 plains the ridges described above, for the roots are frequently a 

 foot below the surface, and the action of fresh water following 

 down the shoots, and probably, also, the action of the juices of 

 the plant, have slightly dissolved the calcareous material and then 

 cemented it into a rock harder than the surrounding deposit. 

 The latter, when erosion commences, wears away and leaves the 

 harder ridge standing. The manner in which the ridges are 

 formed, and the holes in the tops of them, all strengthen this 

 conclusion. The triangular spaces enclosed by the ridges are 

 almost identical in appearance with the triangular spaces marked 

 off by the sucker-like roots that cross each other in all directions. 



Rhizomorphs. 



While visiting the quarry at Nassau my attention was drawn 

 to some cylindrical masses of coral rock that apparently hung 

 root-like over the edges of the quarry and were about four feet 

 in length. They were, however, cemented to the wall. I broke 

 one off, and on examining it found that the particles of which it 

 was composed were arranged in a concentric manner about a 

 central axis. On the way back from the quarry I pulled up a 

 small shrub, and found its roots penetrating the rock, which 

 had been eroded so as to leave cylinders surrounding them. 

 Dr. Dolley ' has called attention to these cylindrical and tubular 

 forms, and has explained their formation by supposing that they 

 represent the " ramifications of a now exterminated flora," and 

 also that "the juices of the roots, acting on the sand imme- 

 diately surrounding them, formed a compact layer. Through 

 erosion and subsidence the vegetation was afterward extermi- 

 nated, the looser particles of drift rock worn away, and the sur- 

 face left covered by myriads of tubes of all sizes, formerly occu- 

 pied by plant roots and rootlets." Later, on Spruce Cay, near 

 Nassau, and at many other places, I found a number of these 

 cylindrical projections, some of which contained a small hole in 



'Loc. cit., p. 131. 



