of some Phanerogamic Parasites. 3 1 9 
If one makes a transverse section of a root of Cissus sp ? 
about two or three centimeters in diameter, which is attacked 
by Brugmansia Zippelii , one finds in the cambium, and in 
both phloem and xylem, cells which are clearly distinguish- 
able from the ordinary cells of these tissues by the very large 
spheroidal nuclei which they contain (see Fig. I, a , Pl. XIV, 
and Fig. X, a , PI. XV). Those in the cambium are smaller 
and have thinner walls than those in the phloem and xylem. 
These latter are also more or less deep brown in colour. In 
the xylem, one finds the cells with large nuclei between those 
elements which have only very recently been developed from 
the cambium, or between those in which starch is commonly 
stored. Seldom are they in contact with the ducts. Those 
near the cambium may be attached to one another ; they are 
also rather thin-walled. Those deeper in the xylem are 
generally isolated and thick-walled, especially if they are in 
contact with cells in which there is no starch. In the 
younger phloem, the cells with large nuclei are in rows of two 
or three and are thin-walled ; but in the older phloem they are 
usually isolated and thick-walled, with larger or smaller 
vacuoles. It sometimes happens that one finds a row of six 
or seven of these cells extending from the cambium to the 
older parts of the phloem, and in such cases (see Fig. I, a , 
PI. XIV) the progressive thickening of the walls from those in 
the cambium outward is very noticeable. In the cambium, 
and in both xylem and phloem, these cells are found between 
the ordinary elements of these three tissues, and they exercise 
no pressure sufficient to compress their neighbours. They 
seem so much like normal elements of these tissues that they 
are readily distinguished from them only by their large nuclei, 
and the brownish hue of their contents. 
In a radial section through a bundle of the same root, one 
finds that in the cambium these cells with large nuclei are 
arranged in chains (see Fig. Ill, PI. XIV, and Fig. IV, PI. XV, 
cells in red). That these chains, which do not always run for 
any great distance parallel to the plane of the section, are 
continuous, is demonstrated by serial sections. They branch 
