170 



NATURE 



[Dec. 31, 1874 



Gymnadciiia odoratissiina remained almost entirely over- 

 looked, some specimens of Crambiis couloneUus, Dup.,* 

 being the only visitors I succeeded in observing during 

 several hours. As the possibility of self- fertilisation has 

 been lost by the flowers of this plant, it must be supposed 

 that its cross-fertilisation by insects happens frequently 

 enough to make self-fertilisation useless. Therefore, from 



the rare diurnal visits and from the pale colour of the 

 flowers, I am inclined to infer that G. odoratissima is 

 more adapted to fertilisation by crepuscular and noc- 

 turnal than by diurnal Lepidoptera. 



A curious observation on G. odoratissima remains to 

 be noticed. In this species, as in mnst Orchids, the 

 labellum («', Fig. 58), properly the upper petal, assumes 



I. 



Fig. s^-—Gyiin:ndeii!n ciomlhsh: 

 floiver 7 : iV 

 r : s, sepals 



; /*, A petals ; /' labellum ; n, developed anther : d 

 n, nectary; «', orifice i 



its position as the lower lip by the torsion of the ovary ; 

 but in some specimens which I found, the torsion of the 

 ovary had stopped half way in all the flowers, so that 

 they occupied a transverse position, directing the labellum 

 and the nectary to the right hand, one of the sepals 

 downwards, the other upwards. A slight approximation 

 to this position is shown by Fig. 59 if compared with 



■me flower (r4 : i), with all the' 

 Tioved except the nectary, 

 nthers ; /c, poUinia ; st^ stigma ; 



Fig. 59.— Front view of the & 

 sepals and petals re 

 , viscid discs ; a' n\ rudimentary lateral ; 

 the nectary ; h^ honey.) 



Fig. 58. This e.xceptional imperfection of the torsion of 

 the ovary of G. odoratissima seems to me to be of some 

 mterest, if we compare it with the normal condition of the 

 flowers of Nii^ritdla awriisti folia (Figs. 60-62), in which 

 the ovary is not at all twisted, so that the flowers occupy 

 just the contrary position to what they do in other Orchids. 

 In consequence of this also the function of the upper and 



"■ptre^tlowS'v^^w^dhSf w^h ^'=- "'-^'-^ '^^ fl°-" ^'Zf '"f""'. -!"' 'h= '''•■rflunr 



the labellum (/") in its naturafposi """°^"' ^^ = ''• 



fon, upwards (3 : i). AH letters have the same significapce in Figs. 60, 61, 62, as in Figs. 58, 59. 



Fig. 62 the limit of the honey is marked. 



Fig. 62.— S 

 tary of s 



Kual organs and nec- 

 me flower, in their 

 tural position. 



Ey the dotted lu 



lower sepals and petals is inverted ; the labellum (/), 

 being turned upwards, here protects the organs of fructifi- 

 cation, and the sepals and petals opposite to the labellum 

 (•*■': A- P, Fig. 61) afi"ord a landing-place for insects. When 

 a butterfly inserts its proboscis into the narrow entrance 



' According to Dr. .Speyer's determination. 



of the nectary («' Figs. 61 and 62), it attaches the viscid 

 discs {d. Fig. 62) to its under side ; and when it flies 

 away, the poUinia, in consequence of the drying up of the 

 discs to which they are affi.xed, undergo an upward and 

 outward movement so as to strike the stigmatic surface 

 of the flower next visited. Nigritella has probably in- 



