118 PROTECTION OF POLLEN. 



in particular. The pollen-cases are in these plants borne on squamous or peltate 

 stalks, which are attached to an axis in a manner similar to the scales of a fir-cone. 

 They also possess in common with the scales of a cone the property of closing and 

 bringing their margins into contact when they are moistened, whereas when quite 

 dry they stand away from one another, leaving wide intervening gaps {cf. figs. 226'^ 

 and 226^*5 with figs. 226 ^' and 226 ^S). The pollen-dust which is developed in little 

 spherical pollen-cases on the inner faces of the scales, is very liable to be shaken 

 out of these gaping interspaces, but such an occurrence, as will be presently more 

 fully explained, is only advantageous to the plant if dry weather prevails. In 

 damp weather, and especially during rain, such escape would be equivalent to de- 

 struction of the pollen. To avoid this risk the gaps close up, an operation which is 

 effected by the scales absorbing moisture and swelling until their edges are in con- 

 tact, so that the little pollen-cases attached to their inner surfaces are covered up. 



In the flowers hitherto described the parts adapted to the protection of the 

 pollen from wind and wet are all leaf-structures or scaly or peltate outgrowths 

 from the connectives of the stamens, and the adapted structure is bent or hollowed 

 out, expanded or folded, as the case may be. Another group of floral forms, 

 scarcely less considerable than the foregoing in point of numbers, secures this 

 protection in a still simpler manner by bendings of the stalks and stem which 

 convert bowl and cup-shaped flowers into pendulous bells. Usually the inflection 

 occurs shortly before the blossoming of the flower, and then the flower retains 

 the drooping position so long as its pollen is in need of protection. Man}- 

 Campanulas (e.g. Campanula harbata, C. iJevsicifoUa, G. jmsilla), Solanaceaa 

 and Scrophularinese (e.g. Atropa, Brugmansia, Cestrum, Physalis, Scopolia, 

 Digitalis), Primulacese and Boragineas (e.g. Cortusa, Lysimachia ciliata, Solda- 

 nella, Mertensia, Pulmonaria), Alpine-roses, Winter-greens and Whortleberries 

 {Rhododendron, Moneses, Vaccinium), Ranunculacene and Dryadese (e.g. Aquilegia, 

 Clematis integrifolia, Geum rivals), and many Liliaceous plants (e.g. Fr'diUaria, 

 Galantlius, Leucojum, Convallaria) may be seen with their flower-buds supported 

 on erect stalks and turned to the sky so long as they are closed. But before the 

 flower is quite open the stalk curves downward, and the mouth of the flower is 

 thus directed more or less towards the earth. No sooner has the flowering 

 period expired, and with it the necessity for shielding the anthers concealed 

 in the interior of the flower, than the stalks, in most instances (e.g. Digitalis, 

 Soldanella, Moneses, Fritillaria, Clematis integrifolia, Geum rivale), straighten 

 out again, and the fruit developed from the flower — especially if a dry fruit- 

 is once more borne at the end of an erect stalk. The phenomenon is illustrated 

 in figs. 221 •* and 221 ^ It is common to hundreds of plants belonging to most 

 widely different families, and exhibits a great variety of modifications. The 

 limits of this work forbid our discussing all these secondary forms of adaptation, 

 which vary partly according to the structure of the stem and flower-stalks, 

 partly according to the form and disposition of the leaves, petals, and stamens 

 We can only give a brief account of some of the most striking cases. 



