of some Phanerogamic Parasites . 3 1 3 
in appearance. Surrounding these are ordinary elongated 
parenchyma-cells the lumina of which contain abundant 
protoplasm. Those in the outermost row abut against the 
cortical tissues of the host. If such a section be treated 
as before described with an aqueous solution of aniline-blue, 
the cross-walls of some of these cells immediately outside 
the cambiform cells are coloured blue (see Fig. 17, s'). The 
colour is not intense, for the walls are never much thickened, 
yet it is sufficient to prove the presence of callus. In older 
haustoria it is possible to demonstrate that these sieve-tubes 
unite with the sieve-tubes, their companion-cells with the 
companion-cells, of the host. One sees, too, that these 
haustorial sieve-tubes are connected, at the base of the 
haustorium, by strands of sieve-tubes developed in the inter- 
fascicular parenchyma, with the sieve-tubes of generally two 
bundles in the mother-plant. 
The haustoria of C. epilinum agree, therefore, in structure 
with those of the two species already described. They 
consist of a central cylinder composed of a bi-collateral 
fibro-vascular bundle, two phloems, with cambiform cells 
between, bounding a common xylem ; and a cortex, thick at 
the base, reduced to a single layer of cells near the apex. 
The smaller size of these haustoria, and the correspondingly 
smaller size of their component cells, are the only differences 
between them and those previously described. 
A similar investigation of C. epithymum gives similar results. 
The material at my disposal consisted of Calluna vulgaris , 
Salisb. over which C. epithymum had grown vigorously, 
sending its haustoria into leaves and stems. The haustoria 
were much broader in proportion to their length than in 
the other species, and the cells of the sucker were pro- 
portionally larger. Fig. 18 shows a young haustorium cut 
in a plane not parallel with its long axis, but at right angles 
to the long axis of the stem of the host. Owing to the 
plane of the section and the youth of the haustorium, its 
structure is not completely shown. One finds in this, however, 
that the shaft consists of a cortex and central cylinder ; that 
