214 
BROWN. 
cleus. The arrangement in rows, rather than in tissues, produces 
an appearance not unlike the mycelium of a fungus. The char- 
acter of the individual cells is, however, quite distinct from that 
of fungus cells, which are usually long, vacuolated, and have small 
inconspicuous nuclei. From the features, mentioned above, it 
will be seen that the vegetative cells of Rafflesia manillana are 
quite similar to embryonic cells in higher plants, and except for 
shape, they have an appearance which is quite like that of the 
embryonic cells in the flower. A row of Rafflesia cells in a 
medullary ray is shown in figure 14. In the upper and lower 
parts of the figure are sections of xylem rays between which there 
is a medullary ray. The black spots are medullary ray cells with 
densely staining contents. The cells of Rafflesia are seen as a 
row running transversely across the center of the figure. They 
have deep-gray colored contents and prominent nuclei. 
The cells of Rafflesia manillana, which form the rows in the 
roots of Cissus, are so intimately connected with those of the 
host that they appear to unite with them in forming a continuous 
tissue. The cells of the parasite, when in the cambium, medul- 
lary rays, or the parenchyma of the bark, are frequently dis- 
tinguishable from those of the host only by a difference in size 
and shape, and by the denser contents and more prominent 
nuclei of those of the parasite (fig. 14) . 
The cells of Rafflesia manillana, in the medullary rays of the 
woody cylinder, are usually wider, more densely filled with pro- 
toplasm, and relatively shorter than those in the xylem. Those 
in the region of the sieve-tubes have, in general, a greater 
diameter and denser contents than those in any other portion 
of the root. Those in the sclerenchyma usually contain large vac- 
uoles and little protoplasm. This vacuolation of the cells, when 
among the dead and empty ones of the sclerenchyma, the more 
vigorous appearance of those in the region of the sieve-tubes, and 
the larger size of the ones in the medullary rays as compared with 
those in the xylem would indicate that there is little conduction 
of food material by the vegetative cells of the parasite. 
The cell-rows of Rafflesia manillana run through the tissues 
of the host in all directions, but are more prominent in the 
longitudinal and radial planes of the root than in the tangential. 
Since they run in all directions in the various tissues, and are 
certainly continuous for very considerable distances, it is evident 
that the cells must grow and multiply in all parts of the root. 
Peirce states that the cells of Brugmansia zippelii “grow and 
Ann. Bot. 7 (1893) 291-327. 
