18 COMMERCIAL BOTANY. 



requires very careful filing, so as to enable it to burst more 

 easily ; if this is not done, tlie seed may take months to 

 germinate.'' 



A new source of India-rubber has quite recently been 

 brought to the notice of the Kew authorities under the 

 name of Colombian Rubber, or Colombia Viegex. By 

 this latter name it seems to have been known in English 

 commerce for the last few years, though the origin or source 

 of it has only just been determined at Kew as that of 

 Sapium higlandulosum, a euphorbiaceous plant allied to 

 Manihot Glaziovii, yield i li g Ceara scrap (see pp. 14 and 1.5). 

 The details connected with the discovery of this rubber 

 are fully given in the Xew Bulletin for July, 1890. It 

 is there said that Colombian Rubber has been generally 

 known in commerce from the place of export as " Cartha- 

 gena," and is supposed to have been the produce of species 

 of Castilloa, which may to some extent still be the case. The 

 plants yielding this so-called "Colombia Virgen " rubber, un- 

 like all other known sources of this substance, gi-ow at a 

 high elevation on the Colombian Andes, viz., at fiom 6,000 

 to 8,000 feet above the sea. A report of an examination 

 of this rubber made at the works of the India-rubber 

 Gutta-percha, and Telegraph Works Company, Limited, at 

 Silvertown, was not favourable, in consequence of the 

 presence of a resinous substance ; but a more recent opinion 

 of a well-known firm of rubber brokers of London and 

 Liverpool, is that it " is of a very superior qii.ilitj- indeed," 

 and was valued in May, 18P0, .it about 2s. lid. or 3s. per 

 pound. 



African Rubber (species of Landolphia). — A large 

 quantity of rubber has found its way into the En<rlish 

 market for a long time under the name of African rubber 

 exported chiefly from the West Coast. It was known to 

 be produced from some specie? of Landolphia, climbing 

 plants with thicl.:, woody stems, belonging to the natural 



