Mivart only alludes to two cases, namely the structure of the flowers of orchids, and the movements of climbing plants.

With respect to the former, he says: "The explanation of their ORIGIN is deemed thoroughly unsatisfactory--utterly insufficient to explain the incipient, infinitesimal beginnings of structures which are of utility only when they are considerably developed.

" As I have fully treated this subject in another work, I will here give only a few details on one alone of the most striking peculiarities of the flowers of orchids, namely, their pollinia.

A pollinium, when highly developed, consists of a mass of pollen-grains, affixed to an elastic foot-stalk or caudicle, and this to a little mass of extremely viscid matter.