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 effect. 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, known as Myanthus barbatus, 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 
* Rolfe, R. A. ‘On the sexual forms of Catasetum with special reference to the 
researches of Darwin and others,” Journ, Linn. Soc. Vol. xxv. (Botany), 1891, pp. 206— 
225, 
2 Fertilisation of Orchids, p. 289. 
3 He wrote in one of his letters, ‘‘...the destiny of the whole human race is as nothing 
to the course of vessels of orchids” (More Letters, Vol. 11. p. 275). 
