eee OhCHID REVIEW. 
VoL. XVII.| MAY, 1909. f[No. 197. 
THE EVOLUTION OF THE ORCHIDACE. 
ORCHIDS are universally acknowledged to rank amongst the most singular 
and most modified forms in the vegetable kingdom. . . An examina- 
tion of their many beautiful contrivances will exalt the whole vegetable 
kingdom in most persons’ estimation.—Charles Darwin. 
The celebration of the Darwin Centenary at Cambridge during the 
coming summer affords a fitting opportunity for a review of what is known 
respecting the evolution of the Orchidacez, on a study of which some of 
Darwin’s conclusions were based, and which furnished the materials for one 
of his most fascinating books, On the various contrivances by which British and 
foreign Orchids are fertilised by Insects, and on the good effects of interciossing. 
That work appeared 43 years ago, and since that time our knowledge of the 
family has made great progress, though much still remains to be done before 
we can claim to have an adequate idea of its origin and progressive 
developr ent. 
One might look to the geological record for some clue to the origin of 
the family, but this is practically blank. It is true that Protorchis and 
Palzorchis have been described from fossil leaves found in the Eocene beds 
of Mt. Bolca, Italy, but it is quite doubtful whether they belong to 
Orchidaceze at all, and there is notrace of Orchids inthe remarkable Amber 
flora, which is also of tertiary age. We are thus limited to such evidence as 
can be obtained from existing representatives of the family, and here there 
are ample materials to work with, and a remarkably diversified range of 
structure, both floraland vegetative. 
The family Orchidaceze is the largest among Monocotyledons, and owes 
its peculiarity largely to the irregular development of the flower, which takes 
the form of suppression of some of the parts and the union of the remainder 
into two compound organs, the lip and the column, giving the flower a high 
degree of complexity. The ovary is inferior, and the seeds numerous and 
very minute, with a reticulated seed-coat, and a quite rudimentary embryo. 
Orchids belong to the most highly specialised group of Monocotyledons, 
known as Microspermez, characterised by the inferior ovary, petaloid 
perianth, and nutetous minute seeds with rudimentary embryo. It is 
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