16 TRANSACTIONS OF THE [oct. 18, 
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 erectus). 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- 
ousdeposit. 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 
1 Loc. cit., p. 131. 
