PROTECTION AGAINST UNBIDDEN GUESTS. 235 



under the cuticle. The cuticle is gradually raised up like a blister till it bursts 

 and the sticky matter escapes. Such portions of the stem or flower-stalk resemble 

 limed twigs, and might have been painted with the viscid substance. In the case 

 of definite glands, the secretion, for the most part, diffuses through the walls to 

 the surface, though in some cases the blister-method may obtain here also. Some- 

 times the secretion is freed by actual rupture of the delicate walls of the glandular 

 cells. 



Sticky secretions as protection for flowers against creeping animals occur 

 most frequently on the flower-stalks, or on the main axis of the inflorescence. 

 The popular names of several plants indicate at once their sticky character, as, 

 for instance, the Catchfly (Silene), and the Viscid Lychnis (Lychnis Viscaria). 

 So also, with their botanical names indicative of their adhesive character and 

 of the insects caught by them, e.g. Silene Tnuscipula, Roridula nnuscipula, and 

 the specifications viscidus, viscosus, viscosissimus, glutinosus, and the like — names 

 frequently occurring amongst the Scrophulariacese, Labiatse, Caryophyllacese, and 

 in the genera Ledwm, Gistus, Linum, Aquilegia, and Bobinia. That the pro- 

 tection afforded by these limed stems is essentially floral is particularly well 

 shown in the Caryophyllaceous genera Bianthus, Lychnis, and Silene. The 

 lower portion of the stem in these plants (e.g. Dianthus viscidus, Lychnis 

 Viscaria, Silene muscipula) is green, and shows no trace of the sticky brown 

 coating which is first met with below the pair of leaves subtending the 

 flowering axes. And here it is only the upper portion of the intemode, the 

 portion in the immediate neighbourhood of the flowers that is sticky (c/. 

 flg. 238, p. 154). 



More frequent than a simple sticky coat is the presence of glands and glan- 

 dular hairs on the flower-stalk, or on the outside of the flower itself, to which 

 little animals climbing up the plant become adherent. Of this condition numerous 

 examples are represented in flg. 261. 



A rarely-occurring condition obtains in the flowers of Cuphea micropetala 

 (fig. 262). The petals in this plant are reduced to tiny scales inserted at the 

 top of niche-like excavations of the calyx (fig. 262*). The calyx is tubular and 

 coloured, 22-28 mm. in length, and 6-7 mm. in diameter; at the base behind 

 the ovary it is expanded into a honey-receptacle. The ovary is relatively large 

 and obliquely placed, forming a sort of "elbow" at the point of articulation of 

 the style which touches the upper wall of the calyx- tube (262^). Since the 

 side-walls of the calyx are in close contact with the ovary, the honey-receptacle 

 is cut off from the general cavity of the flower, as it were, by a plug. Right 

 and left in the ovary, however, are two grooves, slightly wider in front; these 

 form (with the calyx) two tiny canals, about half a millimetre in diameter, by 

 which access may be had to the honey-cavity behind the ovary; usually these 

 canals are more or less flUed with honey (cf. figs. 262^ and 262^, the latter 

 showing the orifices of the two canals and elucidating the relations of the 

 parts). To obtain the honey, flying insects must introduce their probosces into 



