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VIII. TheCaoutchouc-containing Cells of Eucommia ulmoides, Oliver. By F. ERNEST 
Weiss, B.Sc., LS. (From the Botanical Laboratory, University College, London.) 
(Plates LVII. & LVIII.) 
Read 21st January, 1892. 
INTRODUCTION. 
Evcouura СІМ OIDES, the * Tu chung" of the Chinese, was named and 
described by Professor D. Oliver in Hooker's * Icones Plantarum * from some dried 
material, including bark, leaves, and fruit, which had been sent to the Royal Gardens, 
Kew, through the instrumentality of Dr. A. Henry. Professor Oliver called attention 
at the time to the most singular feature about the plant—namely, the presence in its 
tissues of innumerable elastie threads of silvery sheen, which become apparent when the 
leaf, bark, or fruit is snapped across and the parts drawn asunder. 
Some of the dried material was handed to me for the investigation of these threads 
and of the cells containing this elastic substance. But little could be made out, except 
that they occurred accompanying the vascular bundles of the leaf, and very abundantly 
in the secondary phloem and in the pericarp. I was therefore very pleased when I 
received from Professor Oliver a second lot of material, which had been brought to Kew 
through the kind offices of Dr. Henry. This material was preserved in spirit, and 
consisted of а large assortment of winter buds in various stages, some only just beginning 
to open, others provided with shoots showing distinct internodes, and with leaves about 
one half the size of the fully developed leaf. Many of these buds were attached to the 
end of the last year's branches, which were therefore entering upon their second year's 
growth. Т have consequently been enabled to study not only the distribution and 
structure, but also the development of the cells containing the curious elastic threads, 
which are so characteristic of the tissues of Ewcommia. 
I was at first inclined to look upon these threads as of the nature of a hardened gum 
or resin. This, however, is not the case, as they are quite insoluble in alcohol, and both 
gums and resins are distinguished by their solubility in alcohol from viscin and 
caoutchouc. 
Weinling t describes visein as an intermediate substance between resin and caout- 
choue, and mentions its occurrence in young parts of Ficus elastica, where it is later 
on replaced by caoutchouc. It has also been described in Euphorbia helioscopia by 
Ohlenschlaeger, who calls it a caoutchouc-like resin. But viscin differs from caoutchouc 
by its solubility in ether, whereas caoutchouc only swells up in that liquid. 
* Hooker, * Icones Plantarum,’ 3rd series, vol. хх. (1890) t. 1950. 
t Weinling, * Planzenchemie, 1839. 
SECOND SERIES.—BOTANY, VOL. III. 2м 
