of some Phanerogamic Parasites . 305 
a part of the dermatogen, the only part which clearly 
differentiates. Its cells become papillate and perform the 
same functions as root-hairs ; they absorb from the surround- 
ing medium and, like root-hairs, exercise a solvent action 
upon what they came into contact with ; but this solvent 
action is much more pronounced than that of ordinary root- 
hairs. The cells of the sucker are, then, physiologically root- 
hairs, but correspond in origin and position, with the cap of 
ordinary roots. The haustorium is otherwise destitute of a cap. 
The question presents itself — How was the bi-collateral 
bundle of the central-cylinder of the haustorium derived ? 
On the facts already at hand only speculations can be based ; 
but it may be hoped that in some Cnscuta the phylogeny of 
the bi-collateral structure will be shown. 
To summarize the whole matter we may say that the 
haustorium of C. americana is morphologically a lateral root, 
since it originates endogenously and grows only at its tip ; 
that it develops into a structure the bi-collateral vascular 
bundles of which are united with the fibro- vascular bundles of 
the mother-plant by two strands of tracheids and two strands 
of sieve-tubes and their companion-cells ; that its xylem and 
phloem unite directly with the xylem and phloem of one or 
more bundles of the host ; that an unbroken connection is 
made between the conducting tissues of the parasite and its 
host. 
As to the distribution of the haustoria along the stem it is 
only necessary to say that they generally occur in groups ; 
that these groups do not consist as a rule of more haustoria 
than there are bundles in the host ; and that by the twining 
of the parasite successive haustoria are made to unite with 
different bundles of the host, thus insuring an abundant 
supply of food. It often happens that the food-supply 
exceeds the demand, and we thus find considerable quantities 
of starch deposited in the cortical parenchyma. Whether this 
is entirely or largely consumed in the processes of flowering 
and setting seed the material at hand is insufficient to 
determine. 
