26 o 
Robertson. — Some Points in the 
II. The Vegetative Organs. 
The first extant figure of Phyllocladus was published exactly eighty 
years ago by L. C. Richard 1 ; it is an exquisite engraving of P. rhomboidalis , 
the only species then known. The main peculiarity of the vegetative 
structure, to which I have already referred, is the reduction of the leaves 
to more or less ephemeral scales, and the development of lateral stem- 
branches into cladodes (Fig. i). The cladodes arise in the axils of leaves, 
and consist not merely of a single flattened lateral axis, but in many cases 
of a whole system of branches fused edge to edge. In fact, in the words of 
Bertrand 2 , ‘ le cladode de Phyllocladus n’est pas, en general, un rameau 
unique, aplati en forme d’expansion foliacee, c’est tout un systeme de 
rameaux tertiaires et secondaires soudes entre eux et au rameau primaire 
sur lequel ils sont nes.’ The veining of the larger limb of the cladode 
in Fig. i shows the complex nature of the organ ; the secondary leaf-traces 
are easily distinguished from the vascular systems of the tertiary lateral 
shoots occurring in their axils. The leaves are best studied in sections 
of the apical leaf-buds, since they soon fall off and are represented only by 
scars (cf. Fig. 6 and Fig. i). The leaves are very simple structures, triangular 
in section, traversed by a single small collateral bundle accompanied by 
a resin passage. There is no differentiation into spongy and palisade 
parenchyma, and in our species I have not observed any stomates. 
Stomates appear also to be absent in the leaves of P. trichomanoides , 
but in P. rhomboidalis I have observed a few. In transverse sections 
of the main axis each leaf-trace is seen to leave the ring of vascular strands 
accompanied internally by two much larger bundles destined to supply the 
axillary branch 3 (Fig. 7). If the branch is followed upwards it is found to 
remain for some little distance fused with the main axis, but the two 
bundles divide to form a small complete ring, so that a transverse section 
may show the main vascular rings and one or more subordinate vascular 
rings side by side with it. If the axillary branch is destined to form 
a cladode instead of a cylindrical axis it becomes much flattened, and the 
arrangement of the bundles resembles (in a simple case) that shown 
in Fig. 2, or some variant on it. The assimilating tissue of the 
cladode shows a slight differentiation, but this is much more marked in 
P. trichomanoides , where there is a fairly distinct development of palisade 
parenchyma on one side. The epidermis is strongly cuticularized, and the 
stomates, which in the three species examined are not confined to 
one face of the cladode, are well protected (Fig. 5). In the cortex of 
1 L. C. Richard, Commentatio Botanica de Conifereis et Cycadeis, 1S26. 
9 C. E. Bertrand, Anatomie comparee des tiges et des feuilles chez les Gnetacees et les 
Coniferes. Ann. des Sci. Nat., v° ser., Bot., t. xx, 1874. 
8 Observed by Th. Geyler, Einige Bemerkungen iiber Phyllocladus , Abhand. der Senckenberg, 
Naturf. Gesellsch., Bd. xii, 1880. 
