446 ME. W. C. WOESDELL ON THE COMPAEATIVE 



fact, that it appears surprising that the plants should be placed by systematists in 

 distinct genera. In view, therefore, of this fact, it will not be necessary to describe the 

 structure of this plant in any great detail. 



The main features of this structure are, as in Macrozamia Fraseri^Miq., the possession 

 of a wide pith, traversed by an anastomosing system of vascular bundles and mucilage- 

 canals ; a number (4 or 5) of vascular cylinders extremely broken up by medullary rays, 

 so as to be composed of distinct wedge-shaped segments, often widely separated from 

 each other; a thick cortex, traversed by innumerable leaf-trace bundles, and l)ouuded on 

 its outer periphery by the leaf-bases. 



I will now proceed to briefly describe the structure in the diflFerent regions of the stem, 

 restricting my remarks to those points only in which the structure differs from that of 

 JIacrozamia Fraseri^ Miq. 



Cortex. 



'J'here is as yet, in this plant, no sign of any formation of periderm at the periphery of 

 the cortex cutting off the leaf-bases ; the tissue of these latter is still fresh and directly 

 continuous with that of the cortex. 



The mass of tracheides, constituting a large bulk of each girdle-leaf- trace bundle, 

 possess reticulate, but never or rarely spiral thickenings, and thus do not present so great 

 a resemblance to protoxylem as is the case in 3Faci'ozcmiia Fraseri, Miq.*. The rest of 

 the secondary tracheides on the lower side of each girdle-trace, wliich may form a 

 considerable thickness of the bundle, possess scalariform pittings on their walls, which 

 may either extend the whole way across the wall, so as to present the appearance of a 

 close spiral, or may form several rows of short pits as in the Ferns (PL XLIII. tig. 1). 



The Fascula}^ Zones. 



In the lower part of the stem about Jive distinct zones or cylinders of vascular tissue 

 are observed (fig. 2) ; thus rather more than in Ilacrozamia Fraseri, Miq. These 

 in the upper and younger part of the stem dwindle to two zones. Here and there 

 large segments or bundles can be seen lying, apparently qiiite out of place and somewhat 

 obliquely, between any two of the rings (fig. 2); these constitute the connections 

 between the successive vascular rings — a function which cannot be discerned from an 

 examination of a single transverse section alone, but can be readily made out from a 

 series of such, as also from a radial section (fig. 3) ; in the ordinary cross-section these 

 strands appear merely as irregularly-placed segments of the rings. In describing the 

 structure of the Macrozamia I omitted to draw attention to their presence, as they were 

 much less obvious in that plant. 



Fig. 2 is a diagrammatic view of a portion of a transverse section of an unknown 

 species of Encephalartos from the collection in the large Kew Museum, and affords an 

 excellent illustration of the general type of vascular structure of this genus as described 

 above. 



* Worsdell, " The Anatomy of the Stem of Macrozamia compared with that of other Genera of the Cycadeffi," 

 Ann. Bot. vol. x. 1896. 



