1 1 6 Worsdell. — On the Comparative Anatomy of 
tracheides and vessels, the terminal walls having sometimes 
one or two conspicuous perforations, at other times only 
a few scattered pits. Parenchyma occurs abundantly around 
and among these elements. Sieve-tubes, companion-cells, 
and phloem-parenchyma are irregularly arranged in large 
numbers, forming a well-developed tissue. 
The stone-cells, which constitute a very characteristic tissue 
in the root of this plant, are of considerable diameter. They 
are scattered irregularly throughout the cortex ; round the 
cylinder they occur in greater quantity, often in groups of 
several together ; here they may have very thick walls. 
A small portion of the root, chiefly some of the outer 
cortical cells, is often injured or destroyed by the invasion 
of a fungus, whose dark brown spores fill the cells in large 
numbers. 
In a longitudinal section the cortical cells of some roots 
appear elongated ; in most, however, they are isodiametric. 
The intercellular spaces are often filled with a brown sub- 
stance, which is probably connected with the fungus above 
described. 
The sieve-tubes and companion-cells are very abundant ; 
the former are of various sizes ; of these the innermost are 
quite short, and differ from the companion-cells which are 
cut off from them only in shape ; those further to the outside 
are much longer — they have either transverse or slightly 
oblique terminal walls, on which are several sieve-plates ; 
there is always a conspicuous callus-layer below the plates, 
which stains well in aniline-blue and Hoffmann’s blue. Sieve 
plates also occur on the lateral wall between two sieve-tubes ; 
none were observed between the latter and companion-cells. 
The younger sieve-tubes have protoplasmic contents and a 
conspicuous nucleus. 
The companion-cells are cut off from the sieve-tube either 
in regular, uninterrupted, vertical rows of narrower or broader 
cells or they may occur isolated, with a curved wall bulging 
out towards the cavity of the sieve-tube, and having more 
or less pointed ends. They are either quite small elements 
