Notes . 
527 
ture between that of the leaf and that of the vegetative stem, which latter is entirely 
devoid of medullary phloem . There was no phloem in the middle of the pith, as is the 
case in the leaf, but at the inner angle of one of the bundles, just at the entrance to 
a medullary ray, I observed a small isolated group of phloem, and I also noticed 
a large group of phloem in two or three of the medullary rays which was in direct 
connexion with, and a continuation of, the ordinary phloem of the cylinder. Both of 
Myristica fragrans , Houtt. 
Fig. 1. Transverse section of vascular cylinder of midrib of leaf-blade showing the groups of 
medullary phloem ( mph ). + , xylem ; ph , normal phloem. 
Fig. 2. Transverse section of segment of vascular cylinder of vegetative stem showing com- 
plete absence of medullary phloem. 
(Both Figs, diagrammatic and x 75.) 
these appear to me to represent fixed stages in the passage of the medullary phloem 
from the pith outwards to the external phloem of the cylinder. 
Holding the view which I do that the present-day structure of the leaf reveals to 
us in so many cases what was the structure of the stem in the not very remote 
ancestors of the plant, I draw the conclusion that Myristica once had internal phloem 
in the stem, but has now lost it, and I go further and say that this medullary phloem 
of the leaf of to-day represents a vestige of a system of complete medullary bundles 
which were characteristic of both stem and leaf. 
The peduncle, an organ which I have found in so many other cases to retain 
a primitive structure which has vanished from the vegetative stem, has in this genus 
partially retained the primitive character of medullary phloem, of which there is no 
trace remaining in the vegetative axis. ’ 
W. C. WORSDELL. 
Kew. 
