78 
Peirce— A Contribution to the 
a considerable distance which, because it lacks haustoria, is 
receiving no nourishment from outside. The distance to 
which food can be transported is dependent, of course, upon 
the nutritiveness of the host and the health of the parasite. 
One might suppose that, were the parasite strong and well 
fed, it would supply to a region in which haustoria had begun 
to form, all the nourishment necessary for their complete 
development, and also for the development of the overlying 
epidermal cells. Such does not seem to be the case, as the 
preceding experiments show. There is a manifest biological 
advantage in this ; for any support which cannot furnish 
nourishment sufficient for the development of these two 
structures would also be innutritious even when the haustoria 
had penetrated it. The parasite tests the nutritiveness of the 
support by the cells most closely in contact with it. If these 
develop, the nourishment which they receive and pass on 
stimulates the associated structures to develop also. If they 
do not develop because of the lack of nourishment from 
without, there is no stimulus and no growth of the associated 
structures ; plainly an economy of material and of energy. 
How comparatively unimportant to the part forming 
haustoria the food which it receives from other parts of its 
own body is, can be plainly demonstrated in the following 
way. Koch 1 pointed out that pieces of the younger parts 
of the parasite, if cut off, behave like the seedlings ; they 
nutate, they make close turns about a host when they come 
into contact with one, they form haustoria. He does not say 
that such ‘ cuttings,’ if one may apply a gardener’s term to 
them, resemble the seedlings in that they too refuse to twine 
about other than nutritious supports, and thus differ from 
their condition when still attached to the parent plant. This 
is, however, not the case ; here the resemblance ends. These 
cuttings, just as if they were still attached to and receiving 
nourishment from the parent plant, will twine closely about 
sticks of wood as well as about a host, and will also begin the 
formation of haustoria. 
1 Loc. cit., 1880. 
