The carved rock crystal depicting a stylized orange tree, set with black onyx and circular and single-cut diamonds, mounted in platinum, 

Please see Hans Nadelhoffer, Cartier, Editions du Regard, 1984, plate 11 for an illustration of this brooch.

According to Nadelhoffer, this pin was made for Jean-Philippe Worth (1856-1926) who was the father-in-law of Louis Cartier. Jean-Philippe, having studied painting with Corot,  was a known aesthete.  Along with his brother Gaston, Jean-Philippe served as the head of the House of Worth, the renowned haute couture salon founded by his father, Charles Frederick Worth. Located at number 7 rue de la Paix,  the epicentre of luxury retailers, the Worth brothers were perfectly situated to cater to wealthy clients ranging from old aristocracy to newly wealthy  bankers and industrialists.  As a result, Cartier's move to 13 rue de la Paix in 1899  was well timed and enabled them to take advantage of the these same wealthy clients who would be looking for  jewels to complement their  Parisian fashions. In 1898, Louis Cartier married Andrée Worth, Jean-Philippe's daughter, thus adding to the synergy  between the two houses .  

A  photograph of Jean-Philippe Worth dressed as an Indian potentate for a masked ball appears in Nadelhoffer, p. 156, pl. 96.

With a wide variety of motifs at their disposal, Cartier's designers created clips and brooches  that could be worn in imaginative ways in order to perfectly complement an outfit.  Going beyond the traditional brooch that could be pinned  on a dress, they created jewels that  could be worn on belts, shoes, or  in the case of the present brooch, a hat.  See Nadelhoffer, p. 193.

Numbered 03011 and vaguely 02066 or 02016. Please note that the rock crystal 'pot' is a later replacement. Besides a small repair to a piece of onyx and some minor scratches, the piece shows wear commensurate with its age. Very well preserved delicate and fine piece of jewellery. In good condition.
"In response to your inquiry, we are pleased to provide you with a general report of the condition of the property described above. Please note that colour, clarity and weight of gemstones are statements of opinion only and not statements of fact by Sotheby's. We do not guarantee, and are not responsible for any certificate from a gemological laboratory that may accompany the property. We do not guarantee that watches are in working order. Prospective buyers should inspect each lot to satisfy themselves as to condition and must understand that any statement made by Sotheby's is merely a subjective, qualified opinion. Prospective buyers should also refer to refer to any Important Notices regarding this sale, which are printed in the Sale Catalogue, in particular to the Notice regarding the treatment and condition of gemstones and to the Notice regarding import of Burmese jadeite and rubies into the US.
NOTWITHSTANDING THIS REPORT OR ANY DISCUSSIONS CONCERNING A LOT, ALL LOTS ARE OFFERED AND SOLD "AS IS" IN ACCORDANCE WITH THE CONDITIONS OF BUSINESS PRINTED IN THE SALE CATALOGUE."