126 Potter . — On the Occurrence of Cellulose in the 
ten days after being felled, the base of a well-grown sound Oak, ap- 
proximately sixty years old, and in this specimen too a considerable 
quantity of cellulose was found in the first years of its growth, and also 
distributed throughout the duramen and alburnum. 
Branches of various other trees were next examined. In the wood 
of Fagus the occurrence of cellulose was equally as strongly pronounced 
(Fig. 3) as in Quercus , if not more so, in trees grown both in the north and 
central parts of England. It occurs chiefly in the broader annual rings 
which exhibit special development during a season of vigorous growth. 
As in the case of Quercus , the cellulose may be found at the very centre 
of the stem, and branches of twenty-five and thirty years both showed this 
peculiarity in the wood of the first and second years of their growth. 
In Aesculus the cellulose, as indicated by the reaction to haematoxylin, 
was not so immediately apparent, and in specimens I first examined it 
was found only in the very young wood, and then quite locally. A further 
study, however, of numerous transverse sections of different trees showed 
it to be fairly prevalent in the growth of other years. The softer wood 
of Aesculus is very different in character to that of the trees considered 
above, and the inner lining of the wood-fibres is represented by a much 
thinner layer than is the case in many of the harder woods. In certain 
parts of the sections a thin lining can be observed inside the fibre-walls, 
which is stained violet with haematoxylin, and this is the most characteristic 
appearance ; but in other regions, quite locally, the violet-blue layer may 
assume a thicker, more gelatinous appearance, and lie quite detached 
and often crumpled in the lumen. This thicker layer sometimes occupies 
a large part of the fibre-lumen, and shades into a paler colour towards the 
middle lamella, being edged inside with a darker line. In one instance 
I found this disposition of the cellulose along a radius extending throughout 
the third to the ninth years, though most noticeably present in the third 
and sixth years, which showed a more vigorous development, while in 
other parts of the annual rings it was entirely absent. In another section 
it was well marked in the spring wood of the current year. The cellulose 
is more generally to be found in the spring than in the autumn wood. 
In Salix the presence of the cellulose lining to the wood-fibres is 
often very pronounced. In one branch, with a diameter of 1.6 cm. and 
containing ten annual rings, cut from a willow growing at the edge of 
a large pond, hardly a single fibre could be detected which did not show 
a broad violet inner layer when treated with chlor-zinc-iodine. Sometimes 
this layer completely closed the lumen of the fibre. In another instance, 
in a branch with a diameter of 3.7 cm., with twelve annual rings, from 
a tree growing upon a hillside with northern aspect, in many of the 
fibres no violet colour due to chlor-zinc-iodine could be observed, and also 
where the edge of the lumen was coloured deep violet this colour gradually 
