COMPARATIVE ANATOMY OF THE CYCADACE X. 445 
protoxylem can be detected in the outermost region of the 
pith. The tracheides of the secondary wood have the usual 
bordered pits. On the inner side of each zone of wood can 
usually be seen the short, angular, irregularly-shaped tracheides 
that were observed in Macrozamia* in a similar position ; they 
often occur in vertical rows, at other times are irregularly 
scattered in the parenchyma. They are the first-formed 
tracheides of the outer, secondary zones of wood, and are of 
the same nature as those of the cortical strands above described. 
They usually have bordered pits on their walls, but often have 
a kind of reticulation instead, which is probably due to the 
absence of the borders in closely-set pits. The phloem of the 
seeondary zones has often only half the thickness of the xylem; 
it contains, as in all Cycads, numerous fibres. 
In both transverse and tangential section the course of the 
leaf-traces through the medullary rays is very well seen. In the 
latter section, where they are transversely viewed, their orien- 
tation is seen to be rather diverse, the xvlem being directed 
either upwards, sideways, or obliquely. 
The structure of the stem, as seen in this plant, is therefore 
an extension, and the ultimate outcome, of the structure observed 
in the much younger plants of Cycas revoluta, Thunb. 
MACROZAMIA SPIRALIS, Mig. 
Young Seedling. 
Two plants, both still attached to the megasporangium, came 
under my investigation, one of which had developed one or two 
foliage-leaves, the other, being much younger, had as yet 
developed none. 
The only points of importance in the anatomy are: the 
similarity in structure of the cotyledons to what obtains in 
Cycas, the absence of any unusual structure in the pith of the 
stem, and the occurrence of obliquely outgoing strands in the 
hypocotyl. 
In the cotyledon the bundles are arranged as in the case of 
Cycas. They are quite collateral in structure, but some amongst 
them are more or less curved. A large amount of centripetal 
xylem is present, some of which extends round to the sides of 
* Worsdell, in Ann, Bot. vol. x. pp. 608, 618. 
