756 Thiselt on- Dyer. —Morphological Notes . 
structure. In some branches, however, instead of the uniform 
brown mass seen in Fig. 3, a band of tissue immediately 
within the periderm was made out to consist of collapsed, 
brown-walled, rather large cells — no doubt withered cortical 
cells of the Cereus — while the more central part appeared to 
represent a different kind of tissue, more thoroughly dis- 
organized. Near the tip of one branch examined, the con- 
dition was better, as shown in Fig. 5. Below the periderm (p.) 
is a zone of brown collapsed cells ( b . t.), probably cortex of 
the Cereus, and the central region is filled with a colourless 
tissue (c. t., shaded in the drawing). Parenchymatous cells 
were not clearly recognizable, but the tissue appeared to con- 
sist of collapsed cells, and gave a cellulose -reaction with 
Schulze’s solution. Numerous small vascular bundles or 
strands of tracheides are present here (v. b.). They are quite 
irregularly placed, and composed chiefly of spiral elements. 
One may assume that the central pale tissue, containing the 
vascular bundles, is a haustorium of the Loranthus . Nothing 
further can be said about its structure except that one of the 
vascular bundles, which was rather larger than the rest ( a . in 
Fig. 5) had an arrangement of its elements suggesting a 
collateral bundle. It is shown more highly magnified in 
Fig. 6 . The rows of cells ( ph .) are not collapsed, but have 
dense contents. They are probably phloem-parenchyma. 
At the tips of branches examined there was no gap in the 
periderm. While the haustorium was growing in length, of 
course its apical region must have been free. The closing in 
of the tip may have occurred after the death of the haustorium ; 
or perhaps after a time the haustorium may have ceased to 
grow in length, and become completely enclosed while still 
alive. The cortical cells of the Cereus , shut in by the periderm 
might, in that case, have afforded nutriment to the haustorium 
for some little time. 
There is a possibility that one or two branches of the speci- 
men might contain roots of the Cereus , instead of, or in 
addition to, haustorial tissue ; for Arloing 1 finds that several 
1 Arloing, loc. cit., p. 32. 
