2 Miss Robertson, Notes on the Anatomy of 



outer part of the stem is thus to some extent intermediate between 

 that of Cycas and Zamia. 



Worsdell has dealt with the anatomy of three species of this 

 genus, and figured a fourth. It may be well for purposes of com- 

 parison with our species to quote very shortly the main results 

 which he has arrived at. 



In M. Fraseri Miq. 1 , he mentions as the most noteworthy 

 characters exhibited by the anatomy of the stem : — 



(i) The well-developed medullary system of bundles. 

 (ii) The anomalous zones of secondary thickening which, to 

 the number of two or three, surround the normal cylinder. 



(iii) The presence of a tertiary cambium, which, arising in 

 isolated places in the parenchyma either between the normal and 

 the first anomalous ring, or between two anomalous rings, forms 

 wood and bast with inverted orientation, such that the xylem is 

 usually directly opposite that of one of the segments of an 

 anomalous ring. 



(iv) The irregularity and displacements of many portions of 

 the vascular tissue, owing to the great expansion of the parenchyma 

 and the medullary rays between the various segments composing 

 the ring. 



Worsdell figures a transverse section of M. Moorei, F. Muell. 2 , 

 possessing the normal vascular ring, one complete anomalous ring, 

 one outside this which is incomplete, and some isolated bundles 

 belonging to a third anomalous ring. 



In M. Denisonii, F. Muell. 2 , of which he examined a plant having 

 a stem diameter of about 1 inch, Worsdell found no medullary 

 bundles. Nor did the plant at this stage possess extrafascicular 

 rings, but in the region of the primary node it had extrafascicular 

 concentric strands, regarded by Worsdell as the first beginnings 

 and foundation of later-formed extrafascicular rings. 



Worsdell has also investigated two seedlings of M. spiralis, 

 Miq. 3 , which shew no extrafascicular zones, and no medullary 

 system of vascular bundles on the stem. He adds, "It is true 

 that I am describing very young plants of this species ; but I feel 

 sure that they are not so young but that if these characters were 

 really possessed by the plant, they would already have given some 

 indication of their presence." 



It should be noted that though the plant whose anatomy is 

 about to be described is now raised to the rank of a separate 

 species under the name of Macrozamia heteromera, both Bentham 

 and Mueller regarded it as an inland variety of the coast species 

 M. spiralis. 



1 Annals of Botany, Vol. x. 1896, p. 601. 



2 Trans. Linn. Soc. Vol. vi. Part n. 1901, p. 112. 



3 Joum. Linn. Soc. Vol. xxxin. 1898, p. 445. 



