THE PRINCIPLE OF COHESION. 57 



already stated, this is congenital, and, as mth the calyx, so 

 with the corolla, the line of junction may be marked by a 

 marginal cord, or the interspace covered with reticulations as 

 in Campanula rotundifolia. 



As in the calyx of many Labiates, so there may be super- 

 numerary cords in the corolla, until they may be greatly 

 increased in number, as in Gonvolvulus Sepium, Digitalis, etc. 

 The cords being straight in the tube may ramify in the 

 lobes, adding thereby marginal veins to the latter, as in 

 Primula and the Gompositce. In this last, the petals are 

 devoid of median nerves, hence the importance of the mar- 

 ginal with their branches up the edges of the corolline lobes. 



It would be superfluous to multiply examples if the 

 principle be understood ; and what I particularly wish the 

 reader to realize is the, so to say, extraordinary plasticity 

 which resides in these organs of flowers, in that they 

 evidently have the power of altering their structure to meet 

 a variety of requirements ; so that if we might compare them 

 to architectural buildings, we might say that the floral 

 Architect at one time saw not only a chance of some orna- 

 mental improvements in a frieze at some particular place, 

 gi-aceful lines of colour or curvature in another ; or, again, 

 flutings, depressions, and elevations, etc., all breaking up any 

 chance of monotony : but cunningly adds elegant buttresses 

 without, as well as runs up ribs of masonry within the 

 walls ; which, while intended to meet particular strains, only 

 add additional charms to the general and harmonious beauty 

 of the entire fabric. 



Cohesion op Stamens — (1) " Adelphous " Filaments. — 

 This occurs in various degrees, from a comparatively slight 

 union at the base, as in Linum usitatissimum, to a short 

 distance from the anthers, as in MalvaceoB and Leguminosce. 

 It is undoubtedly an adaptation to insect agency. 



