мМ 
~l 
— 
OF А CAMBRIDGESHIRE WOODLAND, 
varying from 8 to the deepest shade in the wood, about 0005. Cirewa 
shows a greater external difference between the two extremes, In both the 
mesophyll of the xhade-leaf has the cells arranged with their long axes 
parallel to the surface, with no differentiation into palisade and spongy tissues, 
The vernal species, such ах Primula elatior and Viola Riviniana, growing 
under conditions of very deep shade, show little structural alteration ах com- 
pared with species growing in open parts, except. that the latter are slightly 
more hairy. 
Some of the shrubs show great powers of shade endurance. In Corylus 
Avellana the shade-leaves are much larger and much less hairy, both in leaf and 
petiole ; structurally they show the typical “ shade-leaf " arrangement with the 
palisade cells inclined to the surface and a large intercellular space system. 
Acer campestre, which keeps its leaves on the lower branches under condi- 
tions of more feeble illumination than does Corylus, shows less structural 
modification, though the extremes are very dissimilar. This species shows 
very well the ar "ngement known as “ leaf-mosaie ? in its shade-shoots ; by 
the twisting of the petioles the leaves are brought to lie at right angles to the 
direction of greatest incident light, and this is done in such а w ay that the 
leaves do not overlap one another. 
Another species showing considerable structural modification іх Juncus 
glaucus ; shoots growing in a light-intensity of 0°04 had a diameter about 
1$ times that of shoots in the open. The sclerenchyma was very little 
developed here. 
Viburnum Opulus is а species that will flourish in illuminations as low as 
0:05, but yet shows very little difference structurally between the sun and 
shade forms. 
Among species intolerant of light may be mentioned Fravinus excelsior, 
Viburnum Lantana, Deschampsia ecspitosa, and Hypericum hirsutum. 
With the exception of Deschampsia cwspitosa none of these flourish when 
their leaves are more shaded than about 0:1. Deschampsia persists in а weak 
state in intensities as low as 0:03. Here there is very little structural 
difference : the ridges оп tho leaf are rather further apart and. the whole tuft 
is lessened in size. 
The other species show practically no structural alteration. Fravinus 
avoids being shaded; by its rapid growth it overtops the hazels and only 
produces leaves in its upper part. 
SUMMARY, 
Gamlingay Wood is in a moderately natural state at the present day ; all 
the species growing in it are such as might be expected in a natural woodlan 
under the same conditions. 
It is situated on Boulder Clay, above Gault and Lower Greensand. This 
ә 2 
2p2 
