Physiology of the Genus Cuscuta. 1 1 7 
whose size, peripheral tissues, internal structure, cell-contents 
and secretions, allow their being closely embraced by the 
parasites, their being readily penetrated by the haustoria, the 
speedy union of the conducting-tissues of the haustoria with 
their conducting tissues, while no poisonous effects are pro- 
duced by cell-contents or secretions. The effects on the host 
are mainly physiological, it rarely happening that anatomical 
changes take place in consequence of the presence of haustoria. 
Finally, the haustoria penetrate by means of mechanical 
pressure, of the chemical activity of the pre-haustoria, of the 
chemical activity of the cells at the tips of the haustoria 
proper ; and these processes are aided, and in part shared in, 
by the cushion-cells. 
I wish to express my warmest appreciation of and heartiest 
thanks for the numberless kindnesses which Professor Pfeffer 
and his assistants have constantly shown me in my work. 
Without their suggestions and criticisms but a small part of 
the investigation just described could have been accomplished. 
Leipzig, 
November , 1893 . 
