266 DR. ALLEMAO ON THE ORIGIN, ETC. OF VESSELS IN PLANTS. 
main body of the nucleus or radicle belongs to the descending system of the root. It is 
more natural to conclude, in the case cited by Dr. Allemäo, that the main descending 
shoot growing out of the radicular bulb, and also the subsequent coleorhizal rootlets, are 
productions of that axile portion of the radicle which I have called the “ neorhiza ;" 
and under this point of view it is easy to account for the coleorhizal character of, the 
secondary rootlets in the germination of Ceratocephalus described by St. Hilaire, which, 
as a natural consequence of this structure, would assume that appearance. A very 
singular example of this sort of production is shown by Klotzsch in the germination of 
the seeds of Pistia*, where the many secondary rootlets or branches of the neorhiza force 
their way through the epirhizal covering of the main root, extending it as a coleorhiza, 
in the form of a long cylindrical tube, which at length breaks away, leaving a long sheath 
in the form of a thimble covering the extremity of each growing rootlet, and which 
probably thus performs the function of a spongiole. 
J. MIERS. 
* Uber Pistia. Berlin, 1853. Plate 1. fig. C, D, E. 
EXPLANATION OF THE PLATE. 
Tas. XXVII. 
The explanation of the several figures is given in the text of the Memoir. 
