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- 

 cuses (e.g. Gentiana Ba- 

 varica, Narcissus poeticus, 

 Gladiolus segetwm, 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. 

 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. 2791° and 

 279 11). 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 Umbelliferas, 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 ghtter 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 procunibens 

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



Fig. 281. — Evening Primrose (Oj^nothera biennis). (After Baillon.) 



