304 



NA TURE 



{Jidy 28, 1887 



said above, the motion is provoked by the least possible 

 breath of air. 



I do not remember a mechanism entirely like this 

 elsewhere among either Orchids or other Phanerogams. 

 Many Orchids are provided with long fringes, but these 

 are due to excessive dissection of the sepals (as in 

 Cirrhopetalum), or to hairs — often multicellular — which, 

 however, are non-versatile. Mr. Rolfe, of the Kew 

 Herbarium, reminds me of the case of Bolbophyllum 

 lemniscatu7n. I need not here further mention the extra- 

 ordinary appendages of the sepals : they are figured in 

 the Botanical Magazine, PI. 5967. 



The labellum in P. ornatus is quite small : in Fig. i it 

 is shown at /, but in the lateral view (Fig. 2) it is hidden 

 by the two petals {i.p). Like the labellum in so many 

 allied Orchids, it moves readily on its narrowed neck if 

 touched. The oscillations are performed especially in a 

 vertical plane. 



The usually accepted view as to the meaning of this 

 vibratility is that hinted at by Morren (" Recherches sur 

 le mouvement et I'anatomie du labellum du Megadinium 

 falcatu7nl' 1841, p. 95) and Darwin ("Fertilization of 



Fig. 4. — Transverse section through the edge of a sepal, showhig the inser- 

 tion of one of the vibratile hairs, h.c, cell bearing the hair (part of 

 which is represented); l.e, epidermis of lower side of sepal : 7i.e, epi- 

 dermis of upper side. 



Orchids," p. 171 ) ; i.e. that by the continued motion of the 

 labellum caused by the wind, insects are led from motives 

 of curiosity to visit the flower. This explanation will 

 hardly hold for such a genus as Pleurothallis, where the 

 labellum is extremely small, and its motion would be 

 hardly obvious from outside the flower. Here the label- 

 lum acts rather as a spring-board. The insect entering 

 the flower will lean upon and displace the labellum, 

 which, from the extreme elasticity of its neck, will oscil- 

 late up and down in precisely the same manner as a 

 spring-board would. By this is insured the insect's head 

 being thrust against the stigma or pollen-masses, and the 

 act of pollinization promoted. Sometimes I have found 

 that if the labellum be displaced by gently pressing down- 

 wards it will be retained for a few seconds in the dis- 

 placed position on removing the force. Soon, however, 

 the elastic reaction overcomes the resistance of the sepals 

 (by which it is temporarily jammed), and the labellum 

 flies up again, considerably overstripping its normal 

 position of rest. After one or more small oscillations, it 

 comes to rest. Such a simple experiment as this shows 



well enough how such an arrangement can aid cross- 

 fertilization. ^ I believe this is the chief part played by 

 the vibratile labellum in Bolbophyllum, in which genus 

 the elasticity is especially manifest. This in no way 

 excludes the attractive function suggested by Darwin. 

 This latter could only hold for cases where the labellum 

 is easily visible outside the flower, and for such cases as 

 B. barbigeruni, B. tremuluin, &c., where it is richly 

 plumed. On the other hand, there is no reason why 

 the " spring-board " function should not operate in 

 every case of vibratile labellum ; hence I regard this 

 as its primary significance, whilst the attractive one is 

 secondary only. This is a question which I hope soon 

 to follow up. F. W. Oliver. 



Jodrell Laboratory, Kew. 



CUBIC CRYSTALS OF GRAPHITIC CARBON. 



T N the analysis of a meteoric iron found in 1884 in the 

 ■*• sub-district of Youndegin, Western Australia, and of 

 which two of the four fragments have been generously 

 presented to the British Museum by the Rev. Charles G. 

 Nicolay, Curator of the Geological Museum, Fremantle, 

 I have obtained some crystals, a description of which may 

 be of interest to the students of carbon. 



The crystals were obtained as an insoluble residue on 

 treatment of 8*3200 grammes of the iron with aqua regia: 

 they are bright, opaque, grayish-black, have a metallic 

 lustre, and present forms belonging to the cubic system. 

 As their characters were not recognized as belonging to 

 any known mineral, it seemed unlikely that the nature of 

 the crystals could be completely determined, seeing that 

 the total weight obtained was only 3 milligrammes ; 

 further, two fragments of the iron, weighing 2 and 7 

 grammes respectively, had not yielded a single crystal, 

 and there was thus a possibility of their being so localized 

 in the iron as to render impracticable an increase of the 

 quantity of material available for experiment. 



The crystals were about a hundred in number, the 

 average thickness of the larger ones being i/ioo of an 

 inch. Many of them are sharply defined cubes ; some have 

 their edges truncated by the faces of the dodecahedron ; 

 in others the edges are replaced by rounded faces of a 

 tetrakishexahedron. 



Their hardness is greater than that of rock salt and 

 less than that of calcite : the streak is black and shining. 

 Of four crystals, two sank to the bottom and two re- 

 mained near the surface of a solution having a specific 

 gravity of 2 "12. The crystals are unaffected by acids: 

 heated in a combustion-tube in a current of oxygen, 

 hydrogen, or chlorine, they are unattacked, even when 

 the glass begins to melt. Heated in a platinum capsule 

 with the table-blowpipe, they slowly disappear without 

 flame. Heated with potassium nitrate in a crucible 

 over a Bunsen burner, they are unaltered ; but disappear 

 very slowly, without deflagration, when heated with the 

 table-blowpipe. 



In density, colour, and streak, and in its chemical 

 behaviour, the residual mineral thus bears a close re 

 semblance to native graphite, but it is considerably 

 harder, and it presents itself in well-defined crystals 

 which belong, like those of the other crystaUized form 

 of carbon, the diamond, to the cubic system : terrestrial 

 graphite, when crystallized, is found only as tabular 

 crystals so indistinctly formed that doubt has Ion 

 existed as to whether they should be referred to the 

 hexagonal or monosymmetric system. 



In a paper entitled " Graphite pseudomorphous after 

 Iron Pyrites," Haidinger, in 1846, described some graph- 

 itic crystals which were doubtless similar to those fur- 

 nished by the Youndegin iron : his observation, however, 



' Regarding the nature of the pollinia, and their mode of removal in 

 Plenrothallis, vide Darwin, loc. cit. p. i66. 



