Macrozamia heteromera, Moore. 13 



the veins. It seems to me that in the existence of this tissue we 

 have a confirmation of Worsdell's 1 view that the " accessory trans- 

 fusion tissue" of the leaves of Gycas is a modification of the 

 mesophyll tissue of the leaf, and not, as Lignier 2 supposes, the 

 remnant of a lateral system of dichotomizing bundles such as that 

 found in the leaf of Stangeria. Worsdell describes this tissue in 

 Cycas as follows : — " Stretching amidst similarly elongated cells in 

 the central region of the mesophyll of the leaf, from the midrib 

 to the margin, is a band of conspicuous tracheides, narrow and 

 elongated in shape and with bordered pits on their walls. These 

 bordered pits are mostly of a rather rudimentary type, with wide 

 slit-like pores, but in many of the tracheides nearest the vascular 



bundle they are more typical in appearance They form a loose 



complex of tissue extending along the whole length of the leaf 

 in a plane parallel to its two surfaces." In the mesophyll cells of 

 Macrozamia heteromera lying between the upper and lower 

 palisade layers, we may recognise a conducting tissue which, 

 though far less well differentiated than the " accessory transfusion 

 tissue" of Gycas, has accomplished something in the direction of 

 such differentiation. 



Summary. 



The main points in the anatomy of Macrozamia heteromera brought 

 out by this investigation are : — 



1. The occurrence throughout a large part of the stem of a single 

 extra zone of vascular tissue outside the normal one, and the existence 

 of an increased number of such zones at the extreme base. 



2. The occurrence of a well-developed system of medullary 

 bundles. 



3. The occurrence in both roots and stem of anomalous periderm 

 formations. 



In conclusion I wish to express my indebtedness to Mr Seward for 

 providing the material, and for the advice and help which he has kindly 

 given me throughout my work. 



1 " Transfusion Tissue," Trans. Linn. Soc. Vol. v. Part vin. 1897, p. 308. 



2 Bull, de la Soc. Linn, de Normandie, Ser. iv. Tom. vi. fasc. 1. 



