204 
Transactions of the Royal Society of South Africa. 
stem tissue (fig. 8). This difference in level may sometimes be observed 
in the cotyledons themselves. Fig. 9 shows the cotyledons and the suc- 
ceeding leaf pair cleared in caustic potash. It will be noticed that not 
only do the leaves of each pair differ in size, but also that the leaf-traces 
of the two cotyledons are inserted on the stele of the axis at slightly different 
levels. Decussate leaves are often present at the base of the plant, and may 
appear at other points as well. In the specimen, a part of which is illus- 
trated in fig. 10, the two opposite cotyledons were followed by four evenly 
spaced leaves. After these came five approximately decussate leaf pairs, 
then one whorl of three leaves, and finally eight leaves evenly spaced. Tall- 
stemmed plants growing in shaded situations often show a considerable 
interval between the two leaves of a " pair," combined with a certain 
amount of stem torsion which serves to obscure the phyllotaxy. 
While specimens from the flats are usually wiry and erect-stemmed and 
show typical radial symmetry, the dorsi ventral condition is occasionally 
approximated to, especially in hardy plants where several basal stems form 
a close, erect tuft. On such stems the leaves appear to be shifted slightly 
so as to face towards the periphery of the fascicle (fig. 11). Small plants 
collected in 1918 on sloping ground which had been ploughed over some 
time before and from which all larger plant growth was absent, showed for 
the most part erect stems with radial symmetry. Specimens were, however, 
found in shaded hollows of the uneven soil which exhibited prostrate 
secondary axes and a marked dorsiventrality. In one of these specimens 
the leaves on the shaded side were distinctly larger than those on the 
illuminated side of the stem (figs. 12, 13). This transition from the iso- 
Fig. 7. 
Fig. 8. 
Fig. 9. 
Fig. 10. 
