34 6 
PROFESSOR W. WILLIAMSON ON THE ORGANIZATION 
I have already referred to the second or thin inner layer of the mac rosp oral -wall. 
This is seen at a, in figs. 65, 66, and 66c, but in spores more recently sent to me, both by 
Mr. Spencer and Mr. Binns, I find it yet more conspicuously exhibited in large spores 
like fig. 58. Fig. 70 represents two hairs from another spore in which there appears to be 
a thin outer layer detached from the exterior surface of the spore, but I cannot determine 
whether this was a feature of the living spore or whether it is merely a result of 
mineralization. Some other specimens render this latter suggestion possible. 
Associated with these macrospores both Mr. Blnns and Mr. Spencer have found 
some other very remarkable objects, some of which may be young states of the 
macrospores just described, or they may belong to distinct species of plants. Fig. 72 
represents the exterior of what I presume has been a small macrospore, in which the 
free extremity of each peripheral appendage is trifid ; somewhat similar conditions 
are seen in the yet smaller examples represented in figs. 7 3 and 7 4. It is impossible 
to overlook the striking resemblance of these little objects to the fossil Xanthidia of 
the chalk flints, and to the zygospores of some of the Desmidese. In figs. 7 5 and 7 6 
we have two objects which appear to be of a different nature. Fig. 76 is obviously a 
cavity about '007 in diameter. The figure represents an optical section, whilst the 
faint areolation represents the ends of the cells bounding the cavity but seen a little 
out of focus. Figs. 75, 75a, 75b, and 75c, are apparently examples of the same 
organism, only in them less of the surrounding parenchyma is preserved. The diameter 
of fig. 75 is about '0012; of 75a and 75c about '0111, whilst fig. 75b is about 
'0166. Fig. 75a, 75b, 75c, and 76 are empty; but fig. 75 is filled with small 
parenchymatous cells which have a mean diameter of about '0012. Fig. 75c also 
contains a mass of parenchyma ; some of the cells in the latter specimen are further 
enlarged in fig. 75d, and two of them are there seen to contain three or four 
small rounded spheres, a, which may possibly be reproductive spores of some kind. 
These objects appear to be conceptacles of some kind that have been formed in the 
midst of parenchymatous tissue, but from which they have shown a remarkable 
tendency to become detached with a somewhat definite yet irregular contour.* 
large number of sections of the Halifax material, and amongst them I have found the two very fine 
maerospores represented in figs. 66a, and 66b, and in one of Mr. Spencer’s slides I find the spore, 
fig. 66c. In 66a, which is enlarged 50 times, the endospermic cells are of uniform size, being about 
•003 in diameter. In fig. 66b, these cells are unequal in size, the largest being about the same magnitude 
as in fig. 66a, whilst the smaller ones are ‘0005, a few odd ones being even still more minute. In fig. 66c, 
we find the cavity of the macrospore filled with irregular parenchyma, apparently resulting from the 
successive subdivision of a multitude of free endospermic cells, which are thus forming themselves into a 
prothallus. In the centre of the specimen a small fragment of a barred vessel, which clearly formed no 
part of the endosperm, suggests the possibility that these cells may belong to some algoid plant that has 
found its way into an empty cavity, the fragment of a vessel having been accidentally introduced along 
with the parasites ; but two other specimens correspond so closely with that figured that I see little reason 
for doubting that this parenchyma belongs to the macrospore. 
* Fig. 76b not only exhibits this defined contour, but further shows a tendency in the peripheral cells 
to arrange themselves in fan-shaped or radiating columns at the three points a, a , a. Other specimens 
