46 
central medulla, surrounded by a cylinder of scalariform 
vessels arranged in radiating wedges, very distinctly separated 
by two kinds of medullary rays (primary and secondary), the 
whole being enclosed in a thick bark from the surface of which 
spring numerous large cylindrical rootlets. The vascular 
cylinder gives off numjerous large vascular bundles ol 
scalariform vessels, which proceed outwards, through the 
conspicuous primary medullary rays, to reach the rootlets. 
The dispute between Mr. . Binney and myself resolves 
itself chiefly into three points. 1st. — The structure of the 
medulla of Stigmaria. 2nd. — The source whence the vascu- 
lar bundles sup]3lying the rootlets are derived. And 8rd. — 
The nature of some vascular bundles which both Mr. Binney 
and M. Goeppert have figured as existing within the medulla, 
and one of which is prolonged radially in M. Goeppert’s 
example through a medullary ray. Mr. Binney and M. 
Goeppert believe that the cellular medulla of Stigmaria 
contained bundles of very large scalariform vessels, and that 
those bundles proceeded outwards to supply the rootlets. On 
the other hand, in my 2nd Memoir, referred to by Mr. Binne}^, 
I not only expressed my conviction, but demonstrated the ab- 
solute certainty that such was not their origin. I adhere to 
the same opinion as I previously expressed, and have the 
specimens on the table which prove its correctness* The 
fact that these bundles were derived, not from the medulla, 
but from the vascular wedges of the woody cylinder, was 
illustrated by the figures 4eS, 44, and 47 of the Memoir 
referred to, figures which accurately represent, not conditions 
occasionally met with, but, those which characterise every 
specimen of the true Stigmaria ficoides. In the Memoir I 
further affirm that immediately wfithin the woody cylinder 
there exists a delicate cellular tissue, and state that one of 
my specimens makes it perfectly clear that the entire 
medulla consisted of similar cells, unmixed with any vascu^ 
lar bundles whatever such as were represented in M. Goep- 
pert’s and Mr. Binney ’s figures, and the accuracy of which 
