THE PRINCIPLE OF COHESION. 59 



by such as have proboscides of sufficient length to reach it, 

 corresponding, of course, to each species or genus. 



Papilionaceous flowers being irregular, and visited in but 

 one way, it is only the superior stamen which is free; but the 

 staminal tube is often imitated in other flowers where there 

 may be no cohesion at all, as by the tribe OcimoidecB of 

 Labiates, Collinsiabi color of the ScrophularinecB Sbnd. Polygala, 

 etc. Similarly, in the case of regular flowers, the mona- 

 delphous condition may be closely mimicked by filaments 

 which are stout and sufficiently rigid to form a column. 

 This occurs in Cruciferce, Viola, Convolvulus, Crocus, etc. In 

 some cases, as in Cramhe and Beutzia, the filaments are pro- 

 vided with wing-like structures which render the tube more 

 complete. In orange flowers, a certain amount of cohesion 

 is actually obtained between some of the filaments. 



(2) Syngenesious Anthers. — These, as stated, are not 

 congenitally united, but by simple contact. As with fila- 

 ments, so with these, it is an adaptation to insect fertilisation. 

 Jasione montana furnishes a good instance for an incipient 

 stage where they just unite at their bases only. This cohesion 

 is completed in the genus Synantliera of the same order 

 CampanulacecB, as well as in the sub-order Loheliece. In other 

 cases of true syngenesious anthers there is a complete lateral 

 fusion, as in Lobelia and Compositoi, in Gloxinia and Im- 

 patiens. In all these cases the cohesion is by lateral con- 

 tact only, and not congenital ; that is to say, the papilh^e of 

 the future anthers on emerging from the axis grow to a 

 somewhat considerable stage of development as incipient 

 anthers before coming into contact. They then coalesce, 

 apparently by a slight solution of the surface of the cellular 



carries a triangular flap, which exactly covers the orifice leading to the 

 honey. A somewhat similar flap occurs in the petals of Phascolus and 

 Delphinium, which likewise keeps out unwelcome guests. 



