96 
Peirce — A Contribution to the 
Unlike the Fungi, which find easier entrance and more 
suitable conditions for growth and development when a plant 
is ailing, Cuscuta flourishes the better in proportion as the 
hosts are stronger, healthier, more able to supply it 
abundantly with food without being forced soon to succumb 
to the constant drain. It is a distinct disadvantage to the 
Dodder when its host dies before it has itself come into 
flower and set seed. Its cycle of development is not so 
simple that it can rapidly be run through ; it demands much 
food and strong mechanical support in order that its flowers 
may be advantageously displayed for the visits of insects, 
and that its fruits may successfully disseminate the seeds 
which they contain. Weak hosts cannot nourish well ; hosts 
which easily succumb after being attacked do not afford the 
necessary mechanical support ; and hosts which vegetate for 
only a short season, dying away either to the root or entirely, 
cannot assist in seed-dissemination. 
II. The Penetration of the Haustoria into 
the Host. 
i. Penetration due to Mechanical Force, 
The various conditions affecting the origin and the develop- 
ment of the haustoria of three species of Cuscuta have been 
discussed in the foregoing pages. There remain to be con- 
sidered in this paper the means by which the haustoria 
already formed in the parent plant make their way into the 
host and attach their xylem- and phloem-elements to the 
corresponding elements of its vascular bundles. In my pre- 
vious paper on certain phanerogamic parasites 1 my treatment 
of this part of the subject was regrettably incomplete, because, 
at the time of writing, only alcohol-material was at my dis- 
posal. From the living plants which it has since been my 
good fortune to be able to observe and to experiment upon, 
I am able to add to what I then wrote. 
Manifestly in one or both of two ways only can the parasite 
1 Loc. cit. 
