7 6 9 
Jeffrey.—On the Affinities of the Gemis Yezonia. 
stomatic guard cells appear as two small elements of equal size in the 
centre of the figure. Over them impend the accessory cells, the whole 
stomatic apparatus strongly resembling the similar structures found in the 
leaf of the living Pinus. Above and below the stomatic guard cells and 
their accessory elements is the epidermis, strengthened by the hypodermal 
cells mentioned above. Fig. 7, PI. LXV, shows the surface of the leaf of 
Brachyphyllum in tangential section. Lines of stomata can be clearly seen, 
in some instances separated b}/ rows of elongated hypodermal fibres. To¬ 
wards the lower side of the figure the plane of section dips into the 
mesophyll, while on the sides and above it passes out into the cuticle. 
Fig. 8, PI. LXV, shows the epidermal and hypodermal structure somewhat 
highly magnified. The rows of stomata appear clearly in alternation with 
stripes composed of intervening hypodermal cells. The degree of enlarge¬ 
ment is now sufficient to show that the hypodermal elements have a striated 
condition of the wall which is an artifact due to fossilization. The guard 
cells of the stomata appear as dark lens-shaped bodies on either side of the 
stomatic aperture. On the lower right-hand side, as well as on the upper 
left, the plane of section is deep enough to engage part of the cavities of the 
guard cells. Outside the guard cells lie the accessory cells, which are quite 
generally four in number. Comparison may be made between the two last 
figures and the one made from much less favourable material by Stopes and 
Fujii. 1 The magnification is less than that used in our Fig. 8, so that the 
details of structure stand out less clearly. 
Structure of the Axis. 
The feature of the anatomical structure of the axis which the Anglo- 
Japanese authors most strongly emphasize in connexion with their genus 
Yezonia is the occurrence of irregularly alternating zones of thicker and 
thinner walled wood tracheides, which do not correspond to annual rings. 
Fig. 9, PI. LXV, illustrates this peculiarity with particular clearness for 
Brachyphyllum. There are obviously two successive zones of thin-walled 
and thick-walled tracheides respectively. In Fig. 10, PI. LXV, the same 
feature is shown less clearly in another specimen. Fig. 11, PI. LXV, illustrates 
the same phenomenon under a higher degree of magnification. These 
figures may be compared with Text-fig. 9, A, B, C, D y E } and Text-fig. 10, 
A, B, C, D , of the memoir of Stopes and Fujii cited above. In our 
Fig. 10, PI. LXV, may be distinguished the cortical and medullary sclerotic 
nests, which equally characterized Brachyphyllum and Yezonia , Stopes and 
Fujii. The Anglo-Japanese authors lay considerable stress on the presence 
of a layer of periderm in the outer region of the stem of their genus 
Yezonia. In the upper region of our Figs. 10 and 11, superior to the 
1 Studies on the Structure and Affinities of Cretaceous Plants. Phil. Trans. Roy. Soc., London, 
Series B, vol. cci, PI. 3, Fig. 9. 
