3i6 Williamson . — Anomalous Cells within Tissues 
within the interior of host- cells, which latter almost always 
belong to the cortex of the invaded plant. In a smaller 
number of instances the hosts are the vessels or tracheids of 
fibro-vascular bundles. It is somewhat more than probable 
that these two types of hosts, the cellular and the vascular, 
may have sheltered two distinct types of organism. 
Fig. i represents a fragment of the bark of some unknown 
plant from the productive Halifax beds. It consists of cells 
variable in size and form, which in the figure are enlarged 124 
diameters. Considerably more than the half of these cells 
are more or less filled with smaller cells, which vary greatly 
in size as well as in the way in which they are grouped. 
Thus at a we have one solitary spherical cell of an inch 
in diameter. At the lower part of the host-cell, b> we have a 
group of cells similar to a , the remainder of the host being 
empty. At c we have a host-cell packed with intrusive cells 
of various sizes ; at the upper and lower parts of the cavity 
these cells approximate to about T Iq (all these measurements 
are given in fractional parts of an inch) in diameter ; but those 
occupying its centre are much smaller, averaging about xfo-o* 
At d a host-cell has its cavity densely filled with very small 
cells, approximating to a mean diameter of seVoJ whilst in 
another host-cell belonging to the same fragment of bark, but 
not included in the figure, the intrusive cells average even less 
than y oV 0 ln diameter. 
We thus see that in the fragment from which Fig. 1 is 
taken, numerous host-cells are filled with intrusive ones of 
every size intermediate between an d 7 0*0 0 5 y et their 
aspects, and the way in which they are aggregated, indicate 
that whatever may be their nature, they represent varied 
conditions of some common vegetable organism. Whenever 
free from contact with one another they are perfectly spherical, 
whatever their dimensions ; but they frequently form small 
clustered groups when, mutually compressing one another, 
they exhibit the familiar aspects of parenchymatous tissue. 
Fig. 2 is a single host-cell from the same specimen as 
Fig. 1, enlarged to 262 diameters. It illustrates several 
