594 J. M. MACFARLANE ON VEGETABLE AND aNIMAL CELLS, 
I venture, therefore, to regard it as a general principle that after cell forma- 
tion has ceased, the cell contents (specially the endonucleolus and nucleolus) 
persist in their activity for a shorter or longer period. 
In studying these relative progressions, one or two features strike us :— 
1. The cell wall is growing rapidly in length. 
2. The amount of progression seems to depend greatly on relative nutrition. 
(a) Those which only become multinucleolar are supplied, as far as can be 
judged, with a moderate supply of pabulum, and are still able, in their earlier 
stages at least, to form cells, as proved in Lquisetwm limosum, Heamanthus 
coccineus, &c., where there may be three or four nucleoli in a nucleus which is 
participating in cell division. The multinucleolar (two to seven) is the usual 
condition of parenchymatous cells after cessation of germinal activity. 
(b) Those which progress to the multinuclear state have an abundant 
pabulum ; thus, in large cells round the fibro-vascular bundles, in bast cells and 
laticiferous vessels, there is abundant elaborated material, and I should suppose 
that the same applies in the suspensor of leguminous plants. In the long cells 
of Chara, whose walls are covered ‘by chlorophyll bodies, as also in Yalonia, 
&c., great nutritive supplies must be ever forming. 
3. That wherever we have multinucleated cells these are never forming new 
cells, but, though helping greatly perhaps in general nutrition, are themselves 
the consumers of much elaborated material wherewith to increase the area of 
the cell wall, and to maintain a certain quantity of protoplasm within it. 
4. That multinucleolar and multinuclear cells are not the result of patholo 
gical change, but ensue naturally when cell formation is stopped, the amount of 
progression being to some degree proportionate to the nutritive supply. When 
we say that the change is not pathological, we mean that it neither originates 
new cells nor destroys old ones, so as to interfere with the normal vital func- 
tions of the plant. Further, in stating that the progression is proportionate to 
the nutritive supply, we do not assert that nutrition is the cause of division of 
the nucleolus or nucleus, but simply that material is provided by which the 
energy of the nucleolus is kept up. 
It will thus be seen that I regard the building up of cells to form a definite 
plant or the parts of it, as the result of a force radiating from the cell centre, 
stimulating to division; and either that the energy giving rise to this force is 
equal to producing only a certain amount of tissue, or that it is inhibited or 
resisted by some external force, which prevents it forming an excess of tissue 
when this would tend to pathological change, or to loss of individuality in the 
plant. Also that the most exalted type of cell is one with abundant pro- 
toplasm containing a single nucleus, nucleolus, and endonucleolus; that a 
cell with vacuolated protoplasm, one nucleus, and two to four nucleoli is less 
exalted, while the multinuclear state is the most degraded form of cell, 
