certain Species of the Genus Christisonia. 115 
neighbouring or even opposite out-growths or stalks are seen 
to fuse together at the apex, where a rounded body, like those 
already described, appears, which becomes at length much 
swollen, and from which, as it eventually disintegrates, short 
filaments are seen emerging. It is possible that we have 
here a case of zygospore-formation in the fungus. If the 
sections are placed overnight in a solution (one per cent.) 
of gold chloride, then washed, and allowed to remain some 
time in citric acid in the sunshine, the protoplasm of the 
fungus stains a dark purple colour. Although the fungus 
is essentially intercellular in its distribution, hyphae were 
occasionally observed in some of the cortical cells, and are 
sometimes seen passing through the pits into a stone-cell. 
An endodermis could not be distinguished ; it would appear 
to be more or less interrupted by the aggregation of stone- 
cells in the region where it is usually sought. On treatment 
of a section with strong sulphuric acid the whole of the cortex 
is destroyed with the exception of the stone-cells, two or 
three of the outermost layers, and the fungus in the inter- 
cellular spaces. The cell-walls bordering on these spaces 
appear also uninjured, as if they were cuticularized ; this they 
possibly may be, in order to prevent the inroads of the fungus 
into the cell-cavity. 
We come next to the structure of the central cylinder ; 
in this plant its typical radial arrangement is quite obscured, 
owing to the greater development of the phloem, which here 
forms a continuous outer zone, and the reduced and rudi- 
mentary state of the xylem, which often consists of only 
a few elements occupying the centre of the cylinder or 
scattered irregularly here and there amongst the parenchyma 
(Fig. 4 ci ) ; sometimes one or two elements can be traced 
further out between the phloem-elements, and these appear 
to represent the protoxylem, though no elements of small 
diameter, so characteristic of the protoxylem elsewhere, are 
present. From this very modified structure it thus becomes 
difficult or impossible to ascertain what is the real arrange- 
ment of the cylinder. The xylem-elements consist of both 
