588 J. M. MACFARLANE ON VEGETABLE AND ANIMAL CELLS. 
internode was cut off, its nucleolus showed continued activity, so here also, 
when the three cells of the cortical node have been formed, the internodal 
nucleolus may have proliferated once or twice. But the cortical nodal cells 
themselves do not further multiply. Curiously enough, however, their nucleoli 
follow the example of that of the internode, though necessarily at a somewhat 
later period ; the consequence being that the cortical internodal, and soon after 
the cortical nodal cells, become multinucleolar (figs. 6 and 7) ; and this multi- 
plication of the nucleoli may not unfrequently be succeeded by breaking up of 
the nucleus. 
This remarkable continued activity without ‘new cell formation holds 
throughout the development of all the vegetative parts. 
We turn now to leaf devélopment. Each leaf originates as a lateral out- 
growth from the stem node, the first portion cut off from it forming a leaf apical 
cell, which by repeated transverse divisions forms a row typically of nine cells. 
Of these, the three ‘terminal, as a rule, do not further divide. Each of the 
lower six divide into an upper, the nodal, and a lower, the internodal, leaf 
cells. The nodal cell and its contents proliferate till it forms a peripheral 
layer of from six to ten cells surrounding an inner central cell. These peripheral 
cells bulge out, their nucleoli divide, the nuclei then divide, a very delicate 
spindle or barrel can now and again be detected (fig. 8), and along its centre 
the new cell wall is deposited. The outer cells thus cut off are the so-called 
stipules. In succession an inner layer, ‘“‘the uniting cells” (Sacus), are simi- 
larly produced. Lastly, the cells of what may now be called the middle layer 
divide, first transversely, then longitudinally. The progress of the latter stage 
is well seen in fig. 9, where, after transverse division, the nucleoli of the cells 
are in every phase of preparation for it. 
But during this time the leaf internodes have been exhibiting the same 
tendency to continued nucleolar proliferation which we have already noticed 
in the stem, but in this respect even they have been outstripped by the three 
terminal cells, whose nuclei, even while the stipules were being developed, 
have greatly enlarged, and their nucleoli have broken up into many portions. 
This again is followed at times by breaking up of the nucleus. A little later 
the internodal leaf cells exhibit similar proliferation (figs. 8 and 9). But 
just as we found that the nodes of the stem cortex after finishing their tissue- 
producing work passed into this state, so also the nodal leaf cells exhibit similar 
phenomena. But in saying so I must except the central, uniting, and stipular 
cells, which, while becoming always multinucleolar, never, to my knowledge, 
become multinuclear. The fact of these cells always remaining relatively 
small, give us a probable explanation of this circumstance. 
In tracing the later or multinuclear stages I have found that staining in 
eosin, &c., with previous decolorising of the preparations, enables me more 
