OPENING OF THE PASSAGE TO THE INTERIOR OF THE FLOWER. 211 



In bilabiate corollas, although the individual parts vary a good deal, the imbricate 

 sestivation is constant, though numerous modifications obtain which cannot be 

 described at length here. Two fairly frequent cases, however, must be described, 

 appertaining to the ringent and personate corollas, to be referred to by and by. 

 In the ringent corolla the upwardly-bent median lobe of the lower lip is placed like 

 a lid in front of the corolla-tube, and upon it lie the two lateral lobes of the same 

 lip; these are covered by the downwardly bent upper lip. In the buds of the Ger- 

 mander (Teucrium), the middle lobe of the lower lip is bent up to such an extent 

 that it covers over the anthers like a dome, whilst in those of the flowers of the 

 scrophularineous Snapdragon and Toadflax {Antirrhinum and Linaria) complete 

 closure of the flower is caused by an inflated portion of the lower lip (the so-called 

 palate), this is covered by the upwardly-directed, central lobe of the lower lip, and 

 this again by the two downwardly directed lobes of the upper lip. 



All these obstacles, however, to access to the interior of the flower are soon 

 removed. The petals, having served as protective wrappers to the bud, fall away 

 on the opening of the flower in cases where they have no further function to 

 discharge. This condition, truly, is a rare one, but occurs in the Vine (Vitis). The 

 petals here are valvate in the bud and form a dome-like covering to the stamens 

 and ovary; they are green in colour, not readily distinguishable from the foliage, and 

 of little value as attractive organs for insects. Under these circumstances it is of 

 advantage that they should be got rid of quickly. This is accomplished as follows. 

 The petals separate from the flower at the base, each rolls up spirally, and they 

 remain hanging together by their apices for a while like a hood, which is ultimately 

 thrown ofl" in consequence of the expansion of the stamens. 



This class of opening of flowers is, as stated, rare. In the great majority of 

 cases the petals play a definite part in the later stages of flowering, and are con- 

 sequently retained. Access to the interior of the flower is brought about by the 

 development between the petals of wide slits as in the Eampion (Phyteuma), or, 

 in ordinary eases, by the entire separation of their free ends from one another; the 

 petals, in fact, spread out, and sometimes even become folded back. This separation, 

 of course, corresponds to the position which the petals previously occupied in the 

 bud. Where the aestivation is valvate, the apices of the petals simply fold back like 

 valves; where it is imbricate, the petals become disentangled; where it is plaited or 

 crumpled, the folds or inequalities become smoothed out. Spirally-twisted buds 

 become untwisted, and it may frequently be observed that two or even three different 

 sorts of movement are necessary for a flower to open. 



In this way, in many cases, only a somewhat circumscribed opening arises, leading 

 down to the expanded or tubular interior portion of the flower. In others, again, the 

 whole flower opens widely like a cup or saucer, as in Roses, Anemones, and Peonies. 



The separation of the petals usually happens very quickly. In the Honeysuckle 

 (Lonicera Caprifolium) opening begins with the folding back of the lowest lobe 

 of the corolla, followed by a similar movement of the others, the stamens become 

 liberated and spread like the fingers of a hand. The whole series of movements can 



