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Xylem of Woody Stems . 
The xylem of Fraxinus is somewhat resistent to the action of boiling 
water, the same effect being produced in other woods after a less severe 
treatment ; but it has been selected for illustration because of the certainty 
of obtaining sections not exhibiting incomplete lignification in any part 
before boiling. 
In the case of Aesculus the delignifying action of boiling water is 
well marked. A portion of a healthy stem of Aesculus was procured, 
with a diameter of 2-2 cm. and ten annual rings. Sections containing 
the whole surface were cut by means of a microtome and placed in a 
boiling tube half-filled with distilled water and steamed for two hours 
on three consecutive days. The sections were then treated with chlor- 
zinc-iodine and phloroglucin, and permanent preparations made by staining 
with Delafield’s haematoxylin and Congo-red (Fig. 7 ) and mounting in 
Canada balsam. (Similar preparations to serve as controls were made 
before steaming.) When stained with chlor-zinc-iodine the appearance 
was most striking and in strong contrast to the unboiled sections. Instead 
of only in certain areas, the fibres and wood-cells in nearly every part 
contained a swollen blue-violet-coloured layer, which was frequently broken 
away and lying in contorted shapes in the lumen (see Fig. 7 ), while the 
middle lamella remained yellow ; the walls of the vessels were yellow, 
swollen, and striated, but lined with a faint blue tinge. The action of 
phloroglucin fully confirmed that of chlor-zinc-iodine. The middle lamella 
of the fibres showed the characteristic red, while the inner layers were 
quite white and colourless ; the walls of the vessels also stained red, but 
they were swollen, and a white unstained lining might in some cases be 
detected. The annual rings stood out distinctly red with phloroglucin, but 
when stained with chlor-zinc-iodine the elements composing these rings 
showed the inner layers swollen, striated, and yellow, enclosing a blue lining. 
Prolonged steaming further emphasized these results. 
Sections subjected to discontinuous steaming for six days when stained 
with chlor-zinc-iodine showed the inner layer of the fibres a deep blue- 
violet, much swollen and in many cases obliterating the lumen ; the walls 
of the vessels and tracheides were much swollen and showed distinctly 
violet ; the elements forming the boundary of the annual rings too had 
a well-marked violet lining. With phloroglucin the walls of the fibres 
remained white, and in some cases even the middle lamella refused 
to stain ; in the vessels too there was a distinct inner white layer, the 
medullary rays staining red. 
Among the many stains for lignin, Hegler (’00) has shown that thallin 
sulphate stains the vanilin yellow and phenol the coniferin a blue-green. 
The action of these stains on steamed wood is of importance, and gives 
confirmation of the results already obtained with phloroglucin. Steamed 
transverse sections from the same piece of Aesculus treated with thallin 
K 
