ON THREE FORMS OF CATASETUM TRIDENTATUM. 151 
On the Three remarkable Sexual Forms of Catasetum tridentatum, 
an Orchid in the possession of the Linnean Society. By 
Cnazrzzs Darwin, M.A., F.R.S., F.LS. 
[Read April 3, 1862.] 
Tuer President and Officers of the Linnean Society having kindly 
permitted me to examine the remarkable specimen, preserved in 
spirits in their collection, of an Orchid bearing flowers of two sup- 
posed genera, and known sometimes to bear the flowers of a third 
genus, I have thought that the Society might like to hear a short 
account and explanation of this singular case. The following 
details will hereafter appear in a small work on the ‘ Fertilization 
of Orchids by Insect-agency,’ which I am preparing for early 
publication. 
Botanists were astonished when Sir R. Schomburgk* stated 
that he had seen three distinct forms, believed to constitute three 
distinct genera, namely Catasetum tridentatum, Monachanthus 
viridis, and Myanthus barbatus, all growing on the same plant. 
Lindley t remarked that “such cases shake to the foundation all 
our ideas of the stability of genera and species.” Sir R. Schom- 
burgk affirms that he has seen hundreds of plants of C. tridentatum 
in Essequibo without ever finding one specimen with seedsf, but 
that he was surprised at the gigantic seed-vessels of the Mona- 
chanthus; and he correctly remarks that here we have traces of 
sexual difference in Orchideous flowers. 
The general appearance of the flower of Catasetum tridentatum, 
in its natural position, is given in the diagram, p. 152 (fig. 1) ; 
but the two lower sepals have been cut off. The column is figured 
separately in an upright position, showing the two curious pro- 
longations of the rostellum, or, as I shall call them, the antenne. 
* «Transactions of the Linnean Society,’ vol. xvii. p. 522. Another account, 
by Dr. Lindley, has appeared in the ‘ Botanical Register,’ vol. xxiii. fol. 1951, 
of a distinct species of Myanthus and Monachanthus appearing on the same 
scape : he alludes also to other cases. Some of the flowers were in an interme- 
diate condition, which is not surprising, seeing that in dicecious plants we some- 
times have a partial resumption of the characters of both sexes. Mr, Rogers, of 
River Hill, informs me that he imported from Demerara a Myanthus, but that 
when it flowered a second time it was metamorphosed into a Catasetum. Dr. 
Carpenter (‘Comparative Physiology,’ fourth edition, p. 633) alludes to an ana- 
logous case which occurred at Bristol. 
t ‘The Vegetable Kingdom,’ 1853, p. 178. . 
1 Brongniart states (Bull, de la Soc, Bot. de France, 1855, tom. ü. p. 20) 
that M. Neumann, a skilful fertilizer of Orchids, could never succeed in ferti- 
lizing Catasetum. f 
LINN. PROC.—BOTANY, VOL. VI. M 
