PHYSIOLOGY OF THE FLOATER. 1 1 3 



Pendulous flowers, such as snowdrop, often present an insur- 

 mountable barrier in the form of a slippery curved stalk. Re- 

 flexed bracts and perianth leaves act in a similar way. "We shall 

 see (p. 121) that if an insect is to benefit a flower by its visit, it 

 must, so to speak, go in by the front door. Bees, even such as 

 could get the nectar in a legitimate way, sometimes prefer to bite 

 a hole at the side. Certain gamopetalous corollas are frequently 

 found neatly drilled in this way. The calyx, epicalvx, and bracts 

 often check such a proceeding, either by the toughness of their 

 tissue, or, in the last case, by crowding. It also seems likely that 

 an inflated calyx, like that of the bladder-campion, is a special 

 arrangement for protecting the nectar. Parts of the flower are 

 often so arranged or shaped as to entirely or partly block up the 

 way to the nectar (which lies deep down in the blossom), in such 

 a manner that small insects are unable to get at it. Yery strik- 

 ing examples are afforded by the personate corollas, e.g., that of 

 snapdragon. Only humble-bees are sufficiently heavy and strong 

 to force down the lower lip of this flower. Stamens may also 

 form obstacles. In heath the large anthers serve this end ; in 

 harebell and Canterbury bell, the dilated bases of the filaments. 

 Cinquefoil secretes nectar on the inner side of the concave recep- 

 tacle, and the numerous perigynous stamens slant upwards and 

 inwards, thus forming a roof for it. Narrow or constricted corolla 

 tubes — knobs, ridges, or swellings in the perianth — nectar-con- 

 taining spurs — crowded petals, stamens, and carpels, all these 

 frequently have to do with the protection of nectar from unbidden 

 guests. Still other devices are found. 



(g.) Wingless insects are most active when the clew has evapo- 

 rated, and this is a signal for the closing of many flowers. 



(li.) Some forms again secrete substances in parts away from 

 the flower, which serve to divert the attention of unwelcome 

 insects. Beans and vetches, for instance, possess " extra-floral " 

 nectaries on the stipules, while common laurel, almond, and peach 

 develop them at the base of the leaf-stalk. 



Equally varied are the means of protection against icet and wind. 

 (a.) Many flowers close in unfavourable weather, (b.) Parts of 

 the perianth often form a kind of roof or penthouse which covers 

 over the internal organs, and the efficiency of which is often 

 enhanced by a covering of hairs. Good examples are seen in the 

 hairy calyx and forwardly directed standard (p. 88) of gorse, 

 and the arched upper lip of the dead nettle. The spathe of arum 

 protects an entire inflorescence (fig. 33). Rain will obviously 

 run off the outside of pendulous flowers, such as harebell and 

 snowdrop, without doing them much injury, (c.) Nectar, again, 

 is so slippery in nature, that rain can only with difficulty wash 



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