394 MR. T. W. WOODHEAD ON THE 
leaf from a plant growing in a moist open Oak wood. Fig. 66 
is a transverse section of this leaf. The epidermal cells are 
strongly cuticularized in both outer, lateral, and to a less extent 
on their inner walls. The lower epidermis is slightly cuticularized 
on its outer wall; the palisade consists of large elongated 
cells frequently containing raphides. The cells of the spongy 
parenchyma are large and air-spaces are numerous. Fig. 67 
shows in outline a leaf from a patch growing under the deep 
shade of Sycamore and Beech ; the stems are long, very slender. 
and the plants prostrate, the leaves are very small and exceed- 
ingly ‘thin. Fig. 68 shows a section of one of the leaves in 
which the cuticle is very thin and the cells of the mesophyll, 
although consisting of three layers, are exceedingly small and 
contain few or no raphides, while the stomata on the under 
surface are distinctly raised. 
MERCURIALIS PERENNIS, Linn. Dog’s Mercury. 
This species not only occurs abundantly in damp woods, where 
large patches are developed due to its vegetative mode of 
increase, but is also a common plant of the hedgerows. Fig. 69 
is a transverse section of a leat from a shade-area of Sycamore 
Figs. 69 & 70. 
Transverse sections. Leaves of Mercurialis perennis. 
Fig. 69 from a leaf growing in a sunny situation. 
D [7] 
Fig. 70 M " in shade of Acer and Ulmus. 
and Elm on a damp, clayey soil. The epidermis is thin-walled; 
mesophyll reduced to three rows of cells; air-spaces relatively 
large, with frequent erystal saes beneath the upper epidermis. 
The leaf is very thin. 
