[Crown Copyright Reserve. | 
ROYAL BOTANIC GARDENS, KEW. 
BULLETIN 
OF 
MISCELLANEOUS INFORMATION 
No. 5] [1921 
XIX.—EUCOMMIA ULMOIDES. 
THE TU-CHUNG OF THE CHINESE. 
JOHN PaRKIN, 
Our knowledge respecting Hucommia ulmoides, Oliv. 
has been largely gained from information supplied by 
Professor Augustine Henry, when resident at Ichang in China 
1882-1890, and from the examination of fruiting specimens sent 
home by him during this period.* It is cultivated in the hilly 
regions of Central and Western China, and though reported to 
be wild, has not yet been seen so by Europeans. 
ee is grown by the Chinese for the sake of its bark, 
which they value highly as a drug, so much so that it commands 
a fancy price. To us, however, the bark is attractive on account 
of its containing silky, silvery threads. These can readily be 
made visible by breaking across a piece of bark and gently 
pulling apart the two fragments, which are then seen to be held 
together by numbers of delicate threads. These occur also in 
the leaves and fruits. They have been regarded as elastic, but 
this must be more apparent than real, as the material composing 
them is more akin to gutta-percha than caoutchouc (india- 
rubber). These substances} as a rule occur in the living plant 
in the form of minute globules suspended in a watery medium, 
the two together forming a “ ,’ which is held in elongated 
cells or vessels. Hence have arisen the botanical terms, “ latex ”’ 
and “ laticiferous tube” for the emulsion and receptacle respec- 
tively. Hucommia, however, is exceptional in having its gutta- 
like substance existing in the dry, solid state in the living plant; 
so no milky juice exudes from any part when punctured. It 
shares this peculiarity along with the composite Parthenvum 
argentatum (the source of Guayule Rubber) (Kew Bull. 1907, 
p. 285; 1908, p. 255; 1910, p. 211), and with Chrysothamnus 
nauseosus (Rabbit bush), a Composite plant of Colorado and 
* Oliver, D. Hooker’s eres Plant., xx., 1890, ¢. 1950. Kew 
Bulletin, 1901, p- 89; ont A 
5 § embraci needed for these plant products 
(caoutchouc, gutta- peering balata) of which the significant ingredient is 
a hydrocarbon of the i sgt (CipHj,)x series. “‘ Elastic gum”’ is not 
suitable as only one member of the group is markedly elastic. 
u (78)15088 Wt3i—p20 1000 8/21 E&S 
A 
