Young Plant of Macrozamia Fraserz. 
579 
Summary of Results. * 
We can distinguish, in the axis of such a plant, the following 
regions : 
1. An apical region, where new leaves are formed and gradual growth 
in length occurs (Text-fig. 8, a). 
2. A sub-apical region, where growth in girth is actively occurring. 
This is brought about by a specialized peripheral layer of the central 
plerome, which, dividing only by tan- 
gential walls, adds parenchymatous 
tissue to pith and cortex in a manner 
reminiscent of the formation of 
secondary tissues by a cambium 
(Text-fig. 8, B). 
3. Below this is established a 
collateral vascular cylinder, in which 
the xylem is largely secondary. In 
this region the cortex is differentiated 
into two regions — an inner ‘ cloudy ’ 
tissue and an outer starchy paren- 
chyma (Text-fig. 8, c). 
4. The cambium of the vascular 
cylinder is tangentially extended, and 
xylem and phloem elements which 
now arise partake of this elongation. 
In this region the beginnings of the 
cambium of the anomalous ring are 
first distinguished (Text-fig. 8, D ; 
also Plate XXII, Fig. II). 
5. Irregular transfusion trachei- 
des are formed by the anoma- 
lous cambium, and the connexions 
or ‘ anastomoses * are being estab- 
lished by the normal cylinder. A 
complete although irregular ring is 
fully established — the first anomalous ring— and the cambium of this ring 
forms xylem and phloem in the usual way (Text-Fig. 8, E). 
6 . The phenomenon of tangential stretching makes its appearance in 
the anomalous ring. (Text-fig. 8, F, also Plate XXII, Fig. III). 
7. The cotyledonary node is a region of extreme complexity, and 
marked by distortion of the tissues (Text-fig. 8, G ; also Plate XXII, Fig. IV). 
This may be in some measure due to the fact that there exists at the node 
a definite constriction of the plant axis ; further, that it abuts on — 
T ext-FIG. 8. Y oung plant cut longitudinally 
nearly in the median plane, and treated with 
phloroglucin to bring out xylem. For lettering 
A— 1 see text, x Pr. = periderm ; ' Gr. == 
girdling leaf-trace ; Lt. = longitudinal leaf- 
trace. 
