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differences are slight. The lower leaf shows no change. The 
one above it (f) just showing hyponasty is forming palisade and 
spongy tissues, and corresponds in its anatomy to the outer leaf 
studied April 27th. The next leaf, still folded on the bud, (g)shows 
a layer of palisade tissue and a slight formation of spongy tissue. 
To sum up: in all these cases examined, the leaves, whose upper 
surfaces were appressed against the stem and so had in no case 
been directly exposed to light, showed beginning of formation of 
palisade tissue. The under surface being at this same time ex- 
posed to direct rays of sunlight, formed no palisade tissue whatever. 
Therefore, the results of these observations show that the general 
statements made regarding change in form of tissues in young leaf 
do not always hold true, as the palisade tissue is already formed 
on morphological upper surface before it has been exposed to 
direct sunlight and before the leaf can be turned. 
There remains now the second consideration, namely, to see 
if, after the leaf has been turned, the tissues can be changed. 
Two methods for experimenting were adopted. In the first 
the bud was tied April 30th, so that the leaf could not turn its upper 
Surface to the light (h). On May 6th, six days later, on cross 
sectioning this leaf, the upper surface showed two well formed 
layers of palisade tissue (i). On the morphological under surface 
exposed to light, two rows of palisade tissue were formed, but not 
directly under the epidermis, the layer immediately under the 
epidermis being ordinarily formed cells with intercellular spaces. 
Another leaf, grown normally, was examined the same day, May 
6th, and was found to be typical, that is with two rows of palisade 
tissue on upper surface and very loose spongy tissue on under 
surface. 
The second method adopted was to turn the leaf over on its 
petiole so that the morphological under surface becomes the upper, 
and fasten the leaf with a split match. Owing to the leaf having 
been disturbed at various times, the result was not very success- 
ful. On examination the morphological upper surface turned 
away from the light still showed two rows of palisade tissue, but 
the cells have intercellular spaces as though taking on the nature 
of spongy tissue. The under surface now exposed to light shows 
tissue with less indication of intercellular spaces, but the cells are 
