310 Peirce— On the Structure of the Haustoria 
into which they penetrate. In the pith one finds the ends of 
some of the longest sucking-cells enlarged, and their walls 
applied to the walls of the cells which enclose them. 
The question as to the chemical nature of the solvent by 
which the papillate epidermal cells overlying the young 
haustorium dissolve the walls and contents of the epidermal 
cells of the host, and of the solvent by which the terminal 
cells of the haustorium perforate or entirely dissolve the deeper 
tissues of the host, still remains to be answered. I hope to 
throw some light on the matter in a subsequent paper. 
CUSCUTA EPILINUM, W eihe, and CUSCUTA EPITHYMUM, Murr. 
In 1880 Ludwig Koch published a long and careful paper 1 
in which he describes these two species in all the stages of 
their life-history. He was unsuccessful, however, in finding 
such an elaborate structure in the haustorium, or such intimate 
histological and physiological relations between host and 
parasite as have just been described in C. americana and 
C. glomerata. I have, therefore, ventured to re-examine them. 
The specimens of C. epilinum were grown on Linum 
tisitatissimum , L. The stems of this parasite are considerably 
smaller and smoother than those of the two species which 
I have just described ; they twine from left to right in generally 
long loose spirals, sending haustoria into the leaves as well as 
stems, but making altogether a looser investment of their 
foster-plants than does either of the foregoing forms. The 
haustoria are sometimes grouped along the stem, sometimes 
uniformly distributed. Their origin is deep in the cortex, as 
Koch has clearly shown. As Fig. 17 shows, they resemble in 
form, though considerably smaller, the haustoria of those plants 
with which we have already become familiar. They make 
their way into the host by openings effected in its epidermis 
through the solvent action of the thin -walled, papillate, 
epidermal cells which first come in contact with the host. 
They press through these openings, pushing aside the cortical 
1 L. Koch, Die Klee- und Flachs-seide. Heidelberg, 1880. 
