282 



DEPOSITION OF POLLEN. 



or the teeth of a comb. This is particularly the case if the stigma is lobed, the 

 lobes being fairly large and spoon-shaped, cup-shaped, or like a funnel, and if the 

 insect on entering only touches the edge of the stigmatic lobes with the pollen-laden 

 part of its body. This is the case, for example, in the flowers of many Gentians, 



Narcissi, Gladioli, and Cro- 

 J '^ ij^ cuses (e.g. Gentiana Ba- 



varica, Narcissus poeticus, 

 Gladiolus segetum, Crocus 

 sativus; cf. figs. 279*'^''''). 



The pollen, when depo- 

 sited, is held between the 

 papillae of the stigma like 

 dust on velvet pile or on a 

 brush or comb; nor is it 

 absolutely necessary that 

 the stigmatic papillae should 

 be sticky, though, of course, 

 the power of retention is 

 thus obviously increased. 

 j Some stigmas are beset with 

 transparent papillae, and at 

 the same time are rendered 

 very sticky by a layer of 

 fluid secreted by the surface 

 cells of the stigma, as, for 

 example, in the Sundew 

 (Drosera; cf. 279^° and 

 279 ^^). But such cases are 

 rare on the whole. Usually 

 the velvety stigmas and 

 those beset with long pa- 

 pillae are not sticky, the 

 viscosity being restricted to 

 wart-like and granulated 

 stigmas. Examples of 

 plants with very sticky 

 stigmas are furnished by the Umbelliferae, the Rhododendrons, Bearberries, Ericas, 

 Whortleberries and Cranberries, Winter Greens and Polygonums, the Deadly Night- 

 shade, and Bartsias. A sticky stigma often terminates a thin threadlike style either 

 as a small disc or head, and is the more conspicuous on account of the glitter of 

 its sticky coating than because of its size. In the flower of the Mahogany-tree 

 (Swietenia Mahagoni; see fig. 282 ^) it has the form of a disc, in Azalea procumbens 

 (see fig. 279 ^^) it is slightly convex with five projecting ridges radiating from the 



Fig. 281.— Evening Primrose (CEnothera biennis). (After Baillon.) 



