.4 Parasite of Stigmarian Rootlets. 65 
now incorporated with the Cash Collection in the Manchester 
Museum, Owens College. Its catalogue number is 0 373. The 
rootlet is cut transversely and its section is almost elliptical, the 
greater diameter being about 1^ nun. The rootlet is of normal type 
with a well preserved outer cortex ( o.c .) consisting of some four or 
five layers of cells. The outermost layers are large and polygonal, 
while the inner ones are narrow and tangentially compressed. 
Some of the epidermal cells are slightly flattened, but otherwise 
uninjured and the root shows no signs of having undergone any 
decay previous to mineralisation. The middle-cortex was evidently 
composed of loosely set cells and is consequently as usual defective 
in preservation, the remains of this layer ( m.c .) being collected 
around the central cylinder. These compressed cells have thin cell 
walls and dark contents, the latter being in some cases contracted 
to the centre of the cell space and connected by delicate threads to 
the cell walls. This middle-cortex would seem to have been com¬ 
posed of cells less stellate in character than those often met with 
in this portion of Stigmarian rootlets. The inner cortex has not a 
very distinct boundary, but is found clothing the vascular cylinder, 
the wood of which has slipped somewhat to one side owing to the 
defective phloem. The position of this latter tissue is as usual 
indicated by a large lacuna. A little to one side of this space is a 
curious mass of tissue partly of secondary formation (fig. 67 i.s.t.) 
and suggestive, if one were dealing with a recent rootlet, of an 
effort on the part of the plant to heal up a wound or to protect 
itself against further ravages by some parasitic organism. In one 
or two places the secondary tissue seems in contact with the inner 
cortex, but it seems to have taken its origin from the cells of the 
middle cortex. That a secondary division of cells can arise from 
this layer of Stigmarian rootlets I have shown 1 in another rootlet, 
in which, however, the divisions arose in the outermost layers of the 
middle cortex, while in the present case the inner layers seem to 
have become meristematic. The secondary tissue is fairly regular 
in its median portion, but becomes less regular towards the edges. 
The cells are for the most part narrow and thin-walled and resemble 
closely the cells produced in the formation of callus or wound cork 
in recent plants. 
This secondary tissue has cut off towards the outside a large 
patch of dark and disorganised cells, which are considerably com¬ 
pressed, so that their contents are rendered almost irrecognisable. 
1 F. E- Weiss. Manchester Memoirs, 1901. 
