536 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
of the smaller, dark-coloured cells, the diameters of these latter varying from about 
•0011 to ’0009. In specimen D in the same slide as B, I find many of the thin-walled 
cells (diameter - 0013 to ’0015). Some of these are empty, and have lost some of the 
turgid, rotund form that usually characterises them. Others are more rounded, and 
each one contains, in its interior, one of the smaller, dark-coloured cells (diameter 
•0009 to ’0007). Intermingled with these larger cells are many free examples of the 
smaller ones, which I expect have been liberated from the interiors of the empty 
larger ones. Specimen E only contains a few of the large, tliin-walled cells (diameter 
•0015, '0014). Some of these are empty, two of them contain each a cell, with a 
diameter of about ’0009, and in one other was a single example of the smaller cells 
('00015). Along with these is a very large number of the smaller cells in a free state. 
This specimen is in the cabinet of Mr. Cash. Specimen F is that of which portions are 
represented in fig. 87, and some of the endosporal cells of which are represented in fig. 88, 
enlarged 320 diameters. At a is a portion of the enclosiug endosporal membrane. At b 
are some of the large thin-walled cells (diameter '0013, - 0014). Each of these contains 
an inner cell, having a diameter of from *0009 to ‘0008, whilst each of these inner cells 
again contains, usually adhering to one side of it, a somewhat irregular dark mass of 
rather variable size. Of these larger cells my section of the spore contains about a 
score. But along with them we have 300 or 400 of the smaller, dark-coloured cells, c, 
of somewhat smaller size than those already described, their diameter ranging from 
•00058 to ‘0004. These are aggregated into a loose irregular central group, detached 
from the endosporal membrane, and condensed at its innermost portion into an opaque, 
somewhat defined mass. The true nature of the apparent central membrane f" of 
fig. 46, is now clear enough. It consists of an aggregated layer of these small cells, 
of which the mean diameter is about ’00055. Why they should have assumed so 
much the aspect of a continuous membrane as - they have done is not so clear. 
From the above description I think we may conclude that the large turgid cells, b, 
belong to the earlier stage in the development of this macrospore, and that the smaller 
and far more numerous ones, c, belong to a later stage. The degree of advancement 
in the development of these endosporal structures does not appear to correspond 
exactly with that of the respective exosporal tissues ; still there is sufficient of an 
approximation to such a correspondence to sustain my general conclusion that the 
specimens A, B, C, and I) are all immature spores, whilst E, F, and the crushed 
specimen fig. 46, are highly matured ones. At the same time, A is undoubtedly a 
more advanced growth, so far as the exosporium is concerned, than B, C, and D ; but 
much less so than any of the remaining three, in which the small dark-coloured cells 
are so abundant. The question now arises, What are these dark objects \ That they 
are cells is certain. In many of them the true cell-wall is sufficiently obvious, though 
in most it fits so closely upon its cell contents, as to be almost invisible. I have 
now no doubt that in fig. 46 the outer cell-walls are in contact, and that the trans¬ 
parent ring surrounding each central circular body represents the space between that 
cell-wall and its contents. 
