compared with other genera of Cycadeae . 619 
course, in which a large number of the tracheides of the 
secondary wood become spirally thickened, thus participating 
in the function of the protoxylem. 
7. The structure and mode of action of the periderm at the 
periphery of the cortex, of which the phelloderm is largely 
composed of stone-cells, and produces subsequently a second 
phellogen in its midst. 
It will thus be seen that, although there are many characters 
which Macrozamia has in common with Cycas and other 
genera already described, this genus possesses characteristic 
anatomical features which up to this date have not been 
noticed in the literature dealing with other members of this 
important order. 
In conclusion, I must express my thanks to Dr. D. H. Scott 
for the help and many valuable suggestions which he has 
given me. 
EXPLANATION OF FIGURES IN PLATES 
XXVII AND XXVIII. 
Illustrating Mr. Worsdell’s paper on Macrozamia. 
The following are the abbreviations used in the lettering of the figures : 
p, pith ; mb, medullary bundle ; x, xylem ; ph, phloem ; nr, normal ring ; 
nph , normal phloem ; ar 1 , first anomalous ring ; ar 2 , second anomalous ring ; 
vF, bundles formed by a fourth cambium ; ax x , xylem of first anomalous ring ; 
avb 3 , bundle formed by tertiary cambium ; me, mucilage- canal ; t, ‘ transfusion- 
tracheides’; mr, medullary ray; ct, cortex; g, girdle leaf-trace; lb, leaf-base; 
pd, periderm ; c, cork ; pdm, phelloderm ; pgn , phellogen ; px, protoxylem ; 
spx 2 , spirally-thickened tracheides of the secondary wood ; nx 2 , normal tracheides 
of the secondary wood ; It, leaf-trace. 
Fig. 1. Segment from a transverse section of a stem of Macrozamia Moorei, 
F. Muell., in the Kew Museum, showing the general arrangement of the tissues 
from the pith to the leaf-bases. Natural size. 
Fig. 2. Transverse section of a portion of a similar stem of M. Fraseri, Miq., 
preserved in spirit, showing segments of the anomalous zones of secondary 
thickening, x 1 5. 
Fig. 3. Medullary bundle following a mucilage-canal, showing especially well 
the orientation of the former in the different parts of its course. Diagrammatic. 
T t 2 
