602 DR A. ANSTRUTHER LAWSON ON 
wall is very thin indeed, forming straight lines and sharp angles with those of the 
neighbouring cells. The mother cells lie very close together, forming a dense mass of 
merismatic tissue with no trace of intercellular spaces between them. ‘They completely 
fill the pocket of the anther, and the absence of curvature in the cell walls clearly shows 
the high uniform pressure which the individual cells exert upon one another. The 
cytoplasm appears in the form of a reticulum in section with a fairly uniform mesh. No 
clear volumes of cell sap of any measurable size that might be interpreted as vacuoles 
are present, but, on the contrary, the cytoplasm is uniformly dense with large quantities 
of granular food substances suspended in its meshes. 
The chromatin reticulum or network appears to be made up of a number of very 
fine threads. These threads are finely granular, and appear to interlace and cross one 
another at frequent intervals. They are so long and so fine that it is quite impossible 
to estimate their number even approximately. The number of free ends that could be 
distinguished, however, made it perfectly evident that the number was a large one. 
Although the threads appear to be very finely granular and at places (see fig. 1) appear 
to have a fairly uniform thickness, a close examination reveals the fact that they are 
really not single but double, the two longitudinal portions being incompletely separated 
from one another by elongated vacuolate spaces. 
The nuclei of these mother cells are very much larger than the nuclei in the 
surrounding vegetative tissue. They are almost spherical in form, and the enveloping 
plasmatic membrane marks a sharp line separating the cytoplasm from the nuclear sap. 
The enclosed karyolymph is apparently exerting a high osmotic pressure upon the 
enveloping plasmatic membrane, and as a result the nucleus has a distended and turgid 
appearance. Large and distended as the nucleus appears, the chromatin substance 
is very evenly and uniformly distributed throughout the spherical cavity. The threads 
representing the chromatin in a very finely divided condition are of fairly equal distance 
from one another. This uniformity, however, is interrupted by the presence of one, or 
more frequently two, very large nucleoli. These latter bodies frequently have clear 
vacuole-like areas within them, but, what seems to be more interesting, surrounding each 
nucleolus there is a clear zone of karyolymph into which the chromatin threads do not 
encroach. I have observed this feature of the nucleoli in many other plants besides 
Snulacina. These points are all clearly indicated in fig. 1. 
The large size of the nucleus of these mother cells is due not directly to the 
increase in chromatin substance—although this is no doubt a factor of importance,— 
but rather to the increased amount of nuclear sap which is taken in endosmotically. 
The conditions here are highly suggestive ‘of a correlation between the amount 
of chromatin (which contains osmotically active organic acids) and the amount of 
nuclear sap taken into the nuclear vacuole. But whether such a correlation exists 
or not, it seems quite evident and beyond a mere assumption, that the enlargement 
of the nuclear cavity is the result of an increase in the amount of its contained 
fluid, and this brings about a corresponding increase in the osmotic pressure acting 
