PROTECTION OF POLLEN. 



113 



which lift the cup-shaped limbs of their corollas above the ground in the 

 spring or late autumn, the Gentians of Alpine meadows and their allies of 

 the Centaury genus (Erythrcea), a host of Bell-flowers with erect blossoms 

 (Campanula glomerata, G. spicata, C. Trachelium, Specularia Speculuin, fee.),. 

 the Peonies, Eoses, Flaxes, Opuntias, Mammillarias and Mesembryanthemums, 

 numerous species of the Star of Bethlehem, and Thorn-apple genera (e.g. Ornitho- 

 galum umhellatum, Mandragora vernalis, Datura Stramoniumi). The floating 

 flowers of the Water-lUy (NyTnphcea), and the large flowers which are borne 



^^^^^''* 



Fig. 223.— Protection of Pollen. 



Flowers of Crocus multifidua. On the right, flowers open in the sunshine; on the kft, flowers closed at night or in wet 

 weather. One of the three closed flowers has some of its perianth-leaves removed. 



on the branches of Magnolias also belong to this group of forms. Throughout 



the day when the sun is shining the floral cups or funnels of these plants are 



wide open and often even expanded into stars, whilst swarms of insects hover 



round them; but at dusk when the dew "falls" the petals close up again and 



overlap one another so as to form a case (cf. fig. 223) upon which any amount. 



of dew may be deposited without affecting the interior of the cup. In damp 



or rainy weather these flowers do not as a rule open. Thus the period of their 



being closed coincides with a time when most honey-seeking insects are absent, 



having either gone to rest for the night, or retired to their hiding-places for 



shelter from the wet. 



It is a very interesting phenomenon that petals which close over the anthers 

 Vol. II. 58 



