160 MB. B. TRIMEN ON THE STRUCTURE OF BONATEA SPECIOSA. 



undoubtedly tlie erect process of the labellum. Its sole use and 

 object are so unmistakeable, and its abrupt promiuence seems so 

 foreign to tbe general character of the labellum and petals, that 

 it AYOuld be difficult to find, even in the Orchidean order, a more 

 striking instance of special modification. "VYith the exception of 

 this local development of the labellum, no part of the perianth 

 appears directly to conduce to the fertilization of the flower ; but 

 the extraordinary modification of the columnar organs effects what 

 is required. The lateral petals, which in so many South African 

 OpTirecd are of the utmost importance, are of no direct service in 

 B. speciosa, nor do I perceive the object of their marked posterior 

 development, imless it be the strengthening of the protection 

 afforded to the poUinia by the upper sepal. The prominent and 

 magnificent group of cohering sepals and petals appears to serve 

 the purposes of protecting and supporting the stigmatic processes, 

 and of affording a convenient landing-place for insects. Possibly, 

 too, its singular form may give it some attractive influence. 



I am unable to supply any details as to the extent to which 

 insect fertilization is effected in this Orchid, having had no op- 

 portunity of observing the plant in its native localities. But, 

 presuming the supply of nectar to be good, nothing seems want- 

 ing to ensure very frequent fertilization. The plant to which I 

 have had access was brought from Kuysna, on the southern coast 

 of the colony. 



E. Tbimek. 



tial OiBce, Cape Town 

 October 7, 1864, 



EXPLANATION OF THE PLATE. 



A. Side view of complete flower. 



B. Front view of complete flower, rather from above, 



C. Side view of column, with all the sepals and petals removed except right 



upper petal. 



D. Under surface of labellum, showing cohering lower sepals, and anterior limbs 



of upper petals which cohere with upper surface. (Apices of stigmatic 

 processes visible on either side of central limb of labellum.) 



E. Front view of portion of column (poUinia removed from anther-cells) with 



posterior limbs of upper petals attached, and rostellum cut away to sho-^ 

 erect process of labellum preventing easy access to nectary. 



F. PoUinium in its natural dependent position when attached by viscid dist to 



a pin and withdrawn from anther-case. 



«. *. Upper sepal. \^pl, PoUinia. 



L s. Lower sepals. - c. Caudicle of polliniura. 

 u,p. Upper petals. r, Rostellum. 



I. Labellum. dd. Viscid disks. 



n. Nectaiy. #». Stigmatic surfaces. 



o. Ovarium. »r. Process of labellum. 



