Vegetable organography; or, an analytical description of the organs of plants / by Aug. P. de Candolle. Translated by Boughton Kingdon.

Candolle, Augustin Pyramus de, 1778-1841.

Date:: 1839-1840

Credit: Vegetable organography; or, an analytical description of the organs of plants / by Aug. P. de Candolle. Translated by Boughton Kingdon. Source: Wellcome Collection.

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$Section II. Of Tracheœ, or Spiral and Elastic Vessels. The Spiral Vessels {vasa spiralia)^ or the Tracheæ {tracheæ), or, as Cassini calls them, the Helicules, (PL 2, Fig. 1, a a, 3, 4,) are organs of an entirely peculiar kind, and about the structure of which there has been much dispute. Henshaw discovered them in the Hazel in 1661, that is to say, a year after the com¬ pletion of the microscope by Hook. Malpighi, who first examined them with care, compared them to the tracheæ of insects, which name he has retained : he regarded them as the respiratory organs of plants, and described them as tubes formed of a band rolled spirally upon itself, capable of unrolling with elasticity. The unrolled tracheæ can be easily seen in breaking a young shoot of the Rose or Scabious. A trachea, seen by the naked eye or through a lens, presents the appearance of a brilliant silver band rolled spirally, as a spring in a funnel. Duhamel compares it to a riband which has been rolled round a cylinder, and wFich by its spi¬ ral circumvolutions would form a continuous tube ; Mirbel confirms this opinion of the structure of the trachea, and only adds that the edge of the band is a little thicker than the middle. Hedwig, on the contrary, has described these same organs in a manner entirely different ; he names them Vasa pneumatochymifera, and believes them to be formed of two distinct organs : he thinks that that which was considered to be a band previous to his observations, is a real tube, which is rolled spirally upon another straight and central tube :$