Floral Structure of Orchids 407 



had shown that it is only a touch on the antennae that causes the ex- 

 plosion, while contact, blows, wounding, etc. on other places produce 

 no efiect. This form of flower proved to be the male. The second 

 form, formerly regarded as a distinct species and named Monachan- 

 thus viridis, is shown to be the female flower. The anthers have 

 only rudimentary pollinia and do not open ; there are no antennae, 

 but on the other hand numerous seeds are produced. Another type 

 of flower, kno\\'n as Ilyanthus barhatiis, was regarded by Darwin 

 as a third form: this was afterwards recognised by Rolfe^ as the 

 male flower of another species, Catasetum barbatum Link, an identi- 

 fication in accordance with the discovery made by Criiger in Trinidad 

 that it always remains sterile. 



Darwin had noticed that the flowers of Catasetum do not secrete 

 nectar, and he conjectured that in place of it the insects gnaw a 

 tissue in the cavity of the labellum which has a "slightly sweet, 

 pleasant and nutritious taste." This conjecture as well as other 

 conclusions drawn by Darwin from Catasetum have been confirmed 

 by Criiger — assuredly the best proof of the acumen with which the 

 wonderful floral structure of this " most remarkable of the Orchids " 

 was interpretated far from its native habitat. 



As is shown by what we have said about Catasetum, other 

 problems in addition to those concerned with fertilisation are dealt 

 with in the Orchid book. This is especially the case in regard to 

 flower morphology. The scope of flower morphology cannot be more 

 clearly and better expressed than by these words : " He will see how 

 curiously a flower may be moulded out of many separate organs — 

 how perfect the cohesion of primordially distinct parts may become, 

 — how organs may be used for purposes widely different from their 

 proper function, — how other organs may be entirely suppressed, or 

 leave mere useless emblems of their former existence^." 



In attempting, from this point of view, to refer the floral structure 

 of orchids to their original form, Darwin employed a much more 

 thorough method than that of Robert Brown and others. The result 

 of this was the production of a considerable literature, especially in 

 France, along the lines suggested by Darwin's work. This is the so- 

 called anatomical method, which seeks to draw conclusions as to the 

 morphology of the flower from the course of the vascular bundles in 

 the several parts^ Although the interpretation of the orchid flower 

 given by Darwin has not proved satisfactory in one particular point 



* Bolfe, R. A. ** On the sexual forms of Catasetum with special reference to the 

 rcBearches of Darwin and others," Joum. Linn. Soc. Vol. xxvii. (Botany), 1891, pp. 206 — 

 225. 



2 Fertilisation of Orchid*, p. 2«9. 



* He wrote in one of his letters, " ...the destiny of the whole human race is as nothing 

 to the course of vessels of orchids " (Afore Letters, Vol. ii. p. 275). 



