406 Mr. Bowman on the Parasitical Connection | 
forming a confused mass under the point in contact with the 
fibre. By this system of vessels the food of the parasite is 
doubtless alienated and conveyed along the root-like fibres into 
its subterranean stem ; and from their dispersed and sinuous 
course within the tuber, it is probable the sap may there undergo 
a necessary change. ‘These vessels consist of a close series of 
minute semi-opake oval bodies, and have a moniliform or beaded 
structure. Tas. XXIII. Fig. 3. shows a transverse section of 
a tuber and its central vessels. 
Some of the many tubers I examined, differed materially from 
the rest, and deserve attention, from the light they appear to throw 
upon the nature of the action excited by parasites in general. 
The section Tas. XXIII. Fig. 4. is one of these ; it is divided in 
the direction of the fibre and of the vessels of the Ash root on 
which I found it. The interior of the tuber was more densely and 
uniformly cellular than usual; and instead of the meandering. 
group of beaded ducts in the centre, it had on each side, near its 
circumference, a separate set of anastomozing vessels, strong and 
darker coloured near their contact with the fibre, but becoming 
gradually paler and more delicate as they approached the middle 
and lower portions of the tuber. Each fascicle communicated 
with the fibre by a single detached trunk, and the spaces be- 
tween a few of the larger reticulations only, were transparent ; 
the remainder of the section being much more opake than in 
Tas. XXIII. Fig. 1. & 2. Here also was no trace of the 
funnel-shaped process ; and the only symptom of derangement 
or disease in the bark and alburnum of the Ash root, was a 
number of small globules, mostly detached, but more closely 
congregated beneath the centre of the tuber. Both the funnel 
and dark anastomozing vessels just described, were wanting in 
other tubers ; but they contained the transparent globules, which 
were also seen more perfectly formed in the alburnum under- 
neath. 
