Physiology of the Genus Cuscuta. 59 
of the hands of a watch. The stem of the seedling, like the 
stem of the older plant, as I shall show later, is sensitive to 
contact-irritation for only a short distance from the tip and 
only in the growing part, and the irritability is greatest near 
the middle of the growing region, diminishing rapidly in both 
directions. If, therefore, the stem be brought by its nutation 
into contact with a host so that a non-irritable or only slightly 
irritable part be applied to the host, either no twining will 
take place, or only a loose steep spiral will be formed, until 
the irritable part touches. Then the Cuscuta rapidly forms 
one or more close spirals, the direction of the curved part of 
the stem being as nearly horizontal as possible. As I shall 
show later, the object of these close spirals is two-fold : they 
bring many more points of the stem into intimate contact 
with the host ; and they hold the stem, which would otherwise 
be pushed away from it by its own growth and by the growth 
of the haustoria, closely applied to the host. When such 
close spirals are made, haustorial formation is induced by the 
intimate contact. The origin, structure, and development of 
the haustoria were described and figured in detail in my 
previous paper 1 . Suffice it to say here that the haustoria 
originate, like typical roots, deep in the cortex, break through 
the overlying cortical and epidermal tissues, penetrate into 
the host and, attaching themselves to the vascular bundles, 
draw from them through tracheids and sieve-tubes the various 
solutions which they contain. Exactly how the haustoria 
make their way into the host was one of the questions which 
I set myself to answer, and of this I shall speak at length in 
the second part of this paper. 
One or more turns in a short close spiral having been made 
about the host, the root, unless already dead, and the stem 
below the first point of contact, die quickly, yielding their 
substance as nourishment to the youngest parts of the 
seedling. The root and stem remain for only a short time as 
an empty, dry, shrivelled filament which the wind quickly 
snaps and blows away. The nourishment obtained from them 
1 Loc. cit. 
