CERTAIN DICOTYLEDONOUS AND CONIFEROUS LEAVES. 249 
twos and threes alternate with each other. Near the extreme apex one 
linear series of stomata forms the band. The orientation of the stomatal 
axes is extremely variable—parallel to, at right angles to, aud oblique to the 
long axis of the leaf. The stomata show, however, a most characteristic 
arrangement of cells. The space occupied by the two guard cells is quadri- 
lateral to oval in outline, or occasionally round. The guard cells themselves 
are somewhat ill-defined, partly because they appear to be only weakly 
cuticularised, partly because they become readily destroyed by the chemical 
treatment they undergo. Moreover, they lose clearness because they are 
below the level of the epidermal cells. The guard cells are surrounded by 
four or oceasionally five narrow elongated cells placed end to end forming a 
ring. These accessory cells stain very deeply with methyl green or saffranin. 
The inner wall of each subsidiary cell where it bounds the guard cells is 
strongly thickened, as are the radial walls also. The stomata occur on both 
surfaces of the leaf. 
Epidermal Cells.—One or two rows of epidermal cells occur between 
the two or three rows of stomata in a band. The epidermal cells occurring 
between two stomata in one linear series are elongated in the horizontal 
direction, i.e., at right angles to the long axis of the leaf, while between 
iwo parallel rows of stomata they are elongated more or less parallel 
to the long axis of the leaf. They are thick-walled, and contain numerous 
large, simple round pits which show especially well in the stained sections. 
The walls are straight, not wavy. The midrib consists of 13-20 rows of 
narrow vertically elongated cells, as one passes from apex to base of the 
leaf. 
Measurement of Cells :— 
Stomata. Subsidiary Cells. 
Average length ....... HS '03 mm. ‘024 mm. 
Average width  .................. ‘0175 mm. ‘012 mm. 
Epidermal Cells. 
Between two stomata Between the series 
of a series. of stomata. 
Average length ............... .. ‘025 mm. ‘042 mm. 
Average width .................. ‘012 mm. -Ol mm. 
Diseussion as to the Affinities of Araucarites Göpperti. 
Gardner believed the leaf to be a true Araucaria. The species was founded 
originally on sterile branches from the Eocene Flora of Haering in the 
Tyrol, which were considered to be externally identical with foliage shoots 
of Araucaria excelsa, but Ettingshausen recorded it from Bilin in Bohemia 
under the generic name of Sequoia, and the question now arises as to whether 
the leaf is an Araucaria or a Sequoia. In order to see whether the cuticular 
