I 4 
Saunders.— On the Structure and 
be seen in a very young flower-bud, and shall then trace the 
changes which take place in (a) cell-wall, (/3) nucleus, (y) cell- 
contents, during the period of development from the young 
bud to the fully open flower, noting finally the extent to 
which these changes are dependent on the relative position 
of the cells. 
A. Very young Bud (Fig. 4 ). 
(a) The epidermal cells are cubical to columnar in shape, 
and somewhat smaller than either the sub-epidermal 
cells, or the unmodified parenchymatous cells of the 
septum. 
(a) The external wall (bounding the lumen) is un- 
cuticularised, and at first exhibits a plane surface ; the 
lateral and basal walls are continuously applied to those 
of the neighbouring cells. 
(/3) The nucleus occupies a very large proportion of 
the cell-cavity, it is generally spherical or oval in shape, 
and lies centrally; one, two, or three nucleoli are often 
present. 
(y) The protoplasm occupying the rest of the cell is 
dense and granular, and in that part of it which im- 
mediately surrounds the nucleus minute starch-grains 
very soon make their appearance. 
(b) The histological modifications of the sub-epidermal cells 
are always most marked in those lying immediately 
beneath the epidermis, and gradually become less and 
less so in those lying further from the lumen, so that 
there is no sharply defined boundary between these 
deeper layers and the unmodified parenchymatous cells 
of the septum, but a gradual transition from the one to 
the other. 
(a) The sub-epidermal cells vary considerably in shape, 
but as a rule all three diameters are roughly equal. 
Their arrangement is less regular and compact than that 
of the epidermal cells, and this character becomes 
gradually more marked in the deeper layers, where inter- 
