January, 1922.] THE ORCHID REVIEW. ¥ 
IS THE TWISTING OF THE OVARY IN ORCHIDS A 
SATISFACTORY CHARACTER FOR SYSTEMATIC 
DIFFERENTIATION ? 
By CoLoneEL M. J. GoDFERY, F.L.S. 
HE twisting of the ovary is widely employed as a distinguishing generic’ 
character. Ascherson & Grzebner (Syn. Fl. Mitt. Eur.), include it in‘ 
the diagnoses of Orchis, Aceras, Gy denia and many other genera, and! 
its absence as a character in Nigritella, Epipogon, etc. Rouy (Fl. de France) 
not only uses it in a generic sense, but also as a character to differentiate’ 
the sub-tribe Physurine (ovary not twisted), from the Spiranthine (ovary 
visibly twisted). It is thus given all the force of a genuine morphological 
character of generic, sometimes even of higher, value. 
It may be remarked incidentally that it is not always easy to say 
whether the ovary istwisted or not. Reichenbach, fil., says of Goodyera,: 
ovary twisted in flower, whilst Rouy says ovary not twisted. This 
discrepancy is probably not due to defective observation, but to lack of 
examination of a sufficiently wide range of specimens. I recently examined: 
examples of Goodyera repens and found some ovaries markedly twisted,: 
some slighty twisted and a few straight. Ascherson and Graebner made a 
similar observation with respect to Spiranthes autumnalis (Sym. ii., 885)’ 
—‘*‘ ovaries . . . . mostly sessile, somewhat twisted, but when in the’ 
lower flowers the stalk is somewhat lengthened, then the stalk, not the ovary,- 
is twisted.” 
From this it is clear that in the case of Goodyera and Spiranthes the’ 
twisting of the ovary is of no value asa generic, still less as a sub-tribal: 
character——-—twisted and straight ovaries can be found on the same spike. | 
The twisting of the ovary is a biological function reversing the flower (which is: 
originally lip upwards), causing the lip to point downwards, so as to forma 
convenient platform for insects to alight on. Untwisted ovaries may be due’ 
to one of two causes. First, it may be unnecessary for the flower to be’ 
reversed so as to bring the lip downwards. Thus in Nigritella, which is: 
fertilised by butterflies, the viscid disc to which the pollinia are attached. 
adheres to the wider side of the side of the insect’s proboscis, and in: 
Epipogon, visited by Bombus lucorum, the bee alights on the column, the 
viscid disc becoming fixed to the under surface of its body. These cases 
are rare and exceptional. Secondly, when an ovary is stalked, the stalk, 
owing to its slenderness, twists much more easily than the ovary, and there 
is no need for the latter to twist. When the ovary is sessile, it must do all 
the twisting required. The phrase ‘‘ ovary twisted ” is, in fact, in most cases 
only another way of saying that the ovary is sessile, a character which. 
would hardly be considered of generic importance. 
The twisting of the ovary occurs, not only in terrestrial, but also in. 
