2 10 
Rose Jordan. 
hydrochloric acid and stains like the lignin on adding aniline 
chloride, perhaps as Molisch suggests owing to inclusion of woody 
substances. Wound-gum is a substance constantly met with in 
connection with tyloses. 
Fig. 3 represents part of a large vessel with two tyloses, both 
covered by this gummy substance which has the appearance of 
small rounded globules and renders the tyloses opaque. Between 
the two tyloses the inner wall of the vessel is also lined with the 
same gummy substance. 
The presence of tyloses has often been considered as a patho¬ 
logical phenomenon or as a means of strengthening those vessels 
which are no longer required for conduction. On the other hand 
it has been suggested by Haberlandt 1 that the tyloses may have 
some direct connection with the flow of nutritive substances in the 
plant,—they may either store starch which can afterwards be 
transferred to the vessels, or they may extract certain substances 
from the transpiratory current which passes up the vessels. 
Certainly the tyloses increase the surface of contact between the 
vessels and the adjoining parenchymatous cells. 
If they act as Haberlandt suggests and absorb food-substance 
from the vessels they would be comparable to the companion-cells 
of sieve-tubes, for like the companion-cells they would abstract 
material from the conducting elements and store it for further use,, 
probably in their own vicinity. The material stored would not in 
that case be starch but raw sap. The thickened tyloses described 
in this paper would support the view that they may function as water- 
storage cells, for they are in structure not unlike the storage- 
tracheids (Speichertracheiden) mentioned by Haberlandt (Physio- 
logische Pflanzenanatomie, page 355). These latter occur either as 
end cells of the vascular bundles, where they appear as somewhat 
swollen cells frequently having spirally thickened or pitted walls as 
in Euphorbia Myrsinites, or they may be transformed cells of the 
mesophyll. Spirally thickened water-storage cells occur also in 
the leaves and tubers of several epiphytic orchids and of Nepenthes . 
It is then quite possible that the function of the tyloses is to store 
up water containing food-substances and that the thickening of the 
walls is a protection against extreme variations of pressure, and 
would prevent the collapse of the cells when water is withdrawn 
from them. 
If the comparison of tyloses with the companion cells of sieve- 
1 Physiologiscke Pflanzenanatomie, 1S96, page 283. 
