26 
Address of the President. 
the Fuci, has ascertained that the same holds good in their 
case. 
Thus, then, we are driven either to admit that the essential 
integers of the vegetable organism, — that which may not only 
maintain an independent existence, but may increase and mul- 
tiply both by self-division and a true generative process, — is 
not (as we have hitherto supposed it to be) a cell ; or we are 
constrained to modify our definition of a cell, so as to make it 
include bodies which do not possess the attributes that have 
been hitherto involved in this designation. Whichever we do, 
we should keep constantly in mind the relationship of the two 
objects. For the nucleated particle of protoplasm, although 
not structurally a cell, is a cell j)hysiologically^ possessing all 
its most important functional endowments ; and although it 
may never develop itself into the type of a cell in a few of 
the lowest Protophytes, which pass the whole of their lives in 
this homogeneous condition, yet in by far the greater number 
this simpler state is but transitory, the homogeneous particle 
of protoplasm speedily differentiating itself into a true cell ; 
so that although not a cell actually^ it may be regarded as 
a cell potentially. Instead, therefore, of characterizing the 
simplest type of vegetable organisation as a cell, having a 
distinct membranous envelope and liquid contents, we should 
more correctly describe it as a nucleated particle of protoplasm, 
that may either remain in that low grade of incipient organi- 
sation of which a homogeneousness (approximating that of in- 
organic bodies) is the distinctive feature, or may make that 
first advance in organisation which consists in the differentiation 
of its substance into the more solid envelope and the more 
liquid interior, the cell-wall and the cell-contents. 
Now it is in showing that a process essentially the same takes 
place in the first formation of new organs in the higher plants, 
that the great value and interest of Mr. Wenham's paper con- 
sist. It has usually been supposed that every leaf originates 
in the duplicative subdivision of a certain cell of the axis, and 
that its subsequent extension is due to the continuance of the 
like process of cell-multiplication. Mr. Wenham has shown, 
on the contrary, that (in certain cases, to say the least) the 
leaf originates in a layer of protoplasm, which is in the first 
instance homogeneous, but in which large vacuoles, disposed 
with a certain degree of regularity, soon make their appear- 
ance ; these vacuoles become the cavities of the first cells, 
whilst the plasma between them, acquiring increased consist- 
ence, become the walls of these cells. Sometimes, when one 
of the first-formed vacuoles is unusually large, it is divided 
into two by the extension of a bridge of protoplasm across it ; 
