76 
Peirce. — A Contribution to the 
moisture and contact combined sufficient. One naturally 
inquires if the nourishing character of the host has anything 
to do with the rapid and full development of these structures. 
To answer this question is easy. If, after having induced 
haustoria by contact with a rod of some sort, taking care that 
the contact be only long enough to induce the formation of 
haustoria and not long enough for the innutritiousness of the 
rod to have any repressive effect on them, one inserts the 
branch into a glass tube as above described, closing the tube 
at the bottom with a split and grooved cork, but sealing the 
hole by a few drops of cocoa-butter or a little gardener’s 
wax, and pours into it a decoction of the usual host-plant, 
one sees that the haustoria develop little more, and that the 
epidermal cells are only slightly longer than when they are 
pressing against a rod of glass or wood. Hence it is plain 
that contact lasting until the formation of haustoria has been 
induced, and followed by a supply of nourishment in solution, 
are not sufficient to produce the effects which are evident 
when contact with a host is uninterrupted. 
It must be admitted, however, that there are two quite 
unnatural elements in this experiment, namely : first, the 
superabundance of food immediately available if the plant 
can absorb it, and second, that this food is equally abundant 
on all sides. To eliminate both of these errors I induced 
haustoria to form on a healthy branch of C. europaea by 
contact with a wooden rod, and then substituted for the 
rod a stick of elder-pith, of about the same size, which had 
been soaked for some time in a hot decoction of Impatiens 
Balsamina which, as sections showed, had penetrated for at 
least a millimetre from the surface. I enclosed the branch 
thus wound around the elder-pith in a glass tube as before, 
keeping the air inside moist by means of wet filter-paper, and 
closing both ends by corks. In the course of nine days the 
Cuscuta had continued to wind closely, making in all five 
complete turns about the pith. Along the inner surface of 
these turns were as many haustoria as would normally be 
formed in an equal distance, and gentle pulling showed that 
