276 CONCLUDING REMARKS. Chap. IX. 



the introduction of the pollen-masses attached to the 

 Ijroboscis of a hnmble-bee. In Mormodes ignea the 

 labelluni is perched on the summit of the column^ 

 and here insects alight and touch a sensitive point, 

 causing- the ejection of the pollen-masses. The la- 

 bellum is often deeply channelled, or has guiding 

 ridges, or is pressed closely against the column ; and 

 in a multitude of cases it apjjroaches closely enough 

 to render the flower tubular. By these several means 

 insects are forced to brush against the rostellum. We 

 must not, however, suppose that every detail of struc- 

 ture in the labellum is of use : in some instances, as 

 with Sarcanthus, its extraordinary shape seems to be 

 partly due to its development in close apposition to 

 the curiously shaped rostellum. 



In Listera ovata the labellum stands far from the 

 column, but its base is narrow, so that insects are led 

 to stand exactly beneath the middle of the rostellum. 

 In other cases, as in Stanhopea, Phaloenopsis, Gongora, 

 &c., the labellum is furnished with upturned basal 

 lobes, which manifestly act as lateral guides. In some 

 cases, as in Malaxis, the two upper petals are curled 

 backwards so as to be out of the way ; in other cases 

 as in .acropera, Masdevallia, and some Bolbophyllums, 

 these upper petals plainly serve as lateral guides, com- 

 pelling insects to visit the flowers directly in front of 

 the rostellum. In other cases, wings formed by the 

 margins of the clinandrum or of the column, serve as 

 lateral guides, both in the withdrawal of the pollinia 

 and in their subsequent insertion into the stigmatic 

 cavity. So that there can be no doubt that the petals, 

 sepals and rudimentary anthers do good service in 

 several ways, besides affording protection to the bud. 



The iinal end of the whole flower, with all its parts, 

 is the production of seed ; and these are produced by 



