Bibliographical Notices, 8^5 



pregnatlon of the same flower, they have missed discovering the true 

 process. According to Mr. Darwin, the pollen of one flower is almost 

 invariably employed to fertilize the seeds of another ; and the con- 

 trivances by which this end is attained in diff'erent Orchids appear to 

 us to be amongst the most remarkable presented by the vegetable 

 kingdom. We may select one of the simplest forms of the process, 

 namely that exhibited by Orchis mascula, as this will furnish a clue 

 to the phenomena presented throughout the group. 



In this plant the top of the column is occupied by the single an- 

 ther, containing two pollinia or masses of pollen-grains, which are 

 produced beneath into small slender stalks, each terminating in a viscid 

 disk which is received into the back of the rostellum. The latter, 

 which is the homologue of one of the stigmata, projects from the 

 front of the column in such a manner as partially to fill up the 

 orifice leading into the nectary, and on each side of it are the 

 true stigmatic surfaces of the remaining two stigmata. The viscid 

 disks of the pollinia are surrounded by a fluid which keeps them 

 constantly moist, being protected from atmospheric influences by the 

 rostellum. The action of this complex apparatus is explained, as 

 follows, by Mr. Darwin : — 



" Let us suppose," he says, " an insect to alight on the labellum, 

 which forms a good landing-place, and to push its head into the 

 chamber at the back of which lies the stigma, in order to reach with 

 its proboscis the end of the nectary. ^ . . . Owing to the pouch-formed 

 rostellum projecting into the gangway of the nectary, it is scarcely 

 possible that any object can be pushed into it without the rostellum 

 being touched. The exterior membrane of the rostellum then rup- 

 tures in the proper lines, and the lip or pouch is most easily de- 

 pressed. When this is eff'ected, one or both of the viscid balls will 

 almost infallibly touch the intruding body. So viscid are these balls 

 that whatever they touch they firmly stick to. Moreover the viscid 

 matter has the peculiar chemical property of setting, like a cement, 

 hard and dry in a few minutes' time. As the anther-cells are open 

 in front, when the insect withdraws its head, one pollinium, or both, 

 will be withdrawn, firmly cemented to the object, projecting up like 

 horns. The firmness of the attachment of the cement is very neces- 

 sary, as we shall immediately see ; for if the pollinia were to fall 

 sideways or backwards, they could never fertilize the flower. From 

 the position in which the two polUnia lie in their cells, they diverge 

 a little when attached to any object. Now let us suppose our insect 

 to fly to another flower : .... by looking at the diagram, it will be 

 evident that the firmly attached pollinium will be simply pushed 

 against or into its old position, namely into its anther-cell. How, 

 then, can the flower be fertilized ? This is efi^ected by a beautiful 

 contrivance : though the viscid surface remains immoveably affixed, 

 the apparently insignificant and minute disk of membrane to which 

 the caudicle adheres is endowed with a remarkable power of con- 

 traction, which causes the pollinium to sweep through about 90 

 degrees, always in one direction, viz. towards the apex of the pro- 

 boscis, in the course, on an average, of thirty seconds. Now, after 



Ann, ^ Mac/, N, Hist, Ser. 3. Vol, x. 26 



