Macrozamia heteromera, Moore. 11 



so characteristic of recent Cycads. These consist of a short, 

 thick-walled, basal cell, and a very long, thinner-walled, terminal 

 cell, the latter containing a single nucleus (Fig. 1). These fila- 

 ments have a golden sheen and are sinuous, and adjacent ones 

 take on parallel curves ; the result is that leaf-bases covered with 

 them look as if they were clothed with " crimped " hair. In 

 transverse sections of the petiole of the leaf 3 cms. long these 

 hairs are seen in their young state. The epidermis consists of 

 columnar cells with rich contents and large nuclei. The hairs at 

 this stage are only 151 to 200 micro-millimetres long, while when 

 fully developed their length may be from 0*5 to 1 cm. or even more. 

 The nuclei of the terminal cells of these young hairs are very large 

 and conspicuous and occupy the whole breadth of the cell. In 

 nearly all cases the nucleus is situated about half-way between the 

 base and apex of this cell. At this young stage the hypodermal 

 masses of sclerenchyma so conspicuous in the mature petiole are 

 represented by groups of thin-walled cells, each of which is almost 

 filled by its nucleus. They give the impression of having recently 

 arisen by division. The vascular bundles are represented by 

 strands of meristematic cells in which a certain amount of dif- 

 ferentiation has taken place ; in each bundle a little group of 

 lignified elements (2 to 5, generally 4) occurs about in the middle 

 of the strand, separated by several layers of cells from the 

 periphery of the bundle on the one hand, and from the arc of 

 phloem on the other. The latter is distinguished from the sur- 

 rounding tissue by the large size and comparative emptiness of 

 its cells. A transverse section of a pinna 2'8 mm. long from this 

 leaf shews that the lamina at this stage consists entirely of un- 

 differentiated thin-walled tissue, highly meristematic, and with 

 large nuclei staining vividly with gentian violet. The position of 

 the future vascular strands is just indicated by the manner of 

 grouping of the cells. 



The mature rachis shews a general similarity in structure to 

 that of Dioon edule. Groups of small lignified cells occur under 

 the epidermis. The ground tissue consists of cells which are 

 round in transverse section and rectangular in longitudinal section, 

 and of very various proportions, some being about twice as long as 

 broad, whilst in others the breadth is the greatest dimension 

 (Fig. 5). These cells present the striking peculiarity of being 

 lignified and reticulately thickened or pitted. In transverse 

 section they are seen to be separated by triangular intercellular 

 spaces, and the parts of the cell wall boi'dering on the lacunae 

 are unlignified. In describing the petioles of the different Cycads 

 Vetters 1 mentions Macrozamia as particularly characterised by 



1 Die Blattstiele der Cycadeen, Leipzig, 1884, p. 10. 



