352 Takeda . — Some Points in the Anatomy of 
instead of the central one, becomes a stoma-mother-cell ; then, although 
four cells will be formed by the last division, a cell belonging to the next 
row, which bordered this mother-cell, will function in the place of subsidiary 
cell (cf. Text-figs, i, d). It seems to me that, at any rate in the cotyledon, 
occasionally even such an abnormality occurs as one of the cells of the two- 
celled stage directly becoming a stoma-mother-cell, while only three cells are 
cut off from the initial cell, one of which will become a subsidiary cell 
(Text-fig. 5). 
The Mesophyll. This tissue of the adult leaf has been thoroughly 
described and figured by Hooker (8). In the cotyledon and the young 
leaf examined by me the palisade tissue is feebly differentiated, consisting 
of two layers of cells on the upper surface and of one layer on the other. 
Amongst these cells, or sometimes directly under the epidermis, one often 
finds cells with very scanty contents. A group of those cells also occurs 
on the margin of the cotyledon as well as of the young leaf. These are 
the cells which will later be converted into sclerenchymatous fibres (cf. 
Fig. 9). This can be particularly well traced in the young leaf. 
The centre of the leaf is occupied by thin-walled parenchymatous cells 
with intercellular spaces. They are isodiametric in shape, or more or less 
elongated longitudinally, and locally pitted. These and the palisade cells 
are full of protoplasm with chloroplasts, and constitute chlorenchyma. 
Sykes ( 19 , p. 181) assumes, without however giving any reason, that these 
cells function as water-storage organs. This assumption is, however, im- 
probable, since the presence of the chloroplasts and intercellular spaces, 
as described above, does not admit of such a supposition. 
In the adult leaf minute crystals of calcium oxalate occur in these 
isodiametric cells as well as in some of the palisade tissue bordering the 
former. The crystals are deposited on the cell-wall, but never in the cell- 
lumen. 
