354 



AUTOGAMY. 



coherent, whilst a further condition, which would also render pollination impossible, 

 consists in a lateral inclination or sharp inflection of the style which removes the, 

 stigma out of the way leading to the honey. The eight anthers then stand in front 

 of the spots where honey is to be obtained, and liberate their pollen in turn. A 

 little later half an hour in Evening-primroses, and 24 hours in the large-flowered 

 species of Willow-herb the style straightens itself and takes up a central position 



in the flower, whilst its four 

 branches open back and present 

 themselves in the form of a 

 cross in front of the entrance to 

 the honey. The stigmas remain 

 in this position for a short time, 

 and there is no need to enter 

 into more detail to make it evi- 

 dent that cross - pollination may 

 now be effected by the humble- 

 bees which come in search of 

 honey and bring with them a 

 store of pollen from younger 

 flowers. Soon afterwards, the 

 four stigmas bend or roll back, 

 bringing their receptive tissue 

 into contact with the pollen still 

 adhering to the anthers (see 

 fig. 300, the lower flowers). This 

 act of autogamy is usually pro- 

 moted also by the stamens becom- 

 ing rather more erect and by an 

 inflection of the stalk-like infe- 

 rior ovary in a gentle curve to- 

 wards the ground, the result of 

 which is that the flowers nod, 

 i.e. are half -inverted. 



Of the Ranunculaceae, a few species of Love-in-a-mist (Nigella) exhibit the same 

 kind of contrivance. The flowers are protandrous. The first event to take place 

 after the expansion of the sepals is a bending of the stamens in regular sequence 

 towards the periphery of the flower, whereby the open anthers are posted just 

 above the nectaries full of honey. Insects coming in search of honey must inevitably 

 rub against the anthers in that position and dust themselves with the pollen. 

 After the stamens have all accomplished these movements, the styles, which have 

 hitherto stood stiffly erect and stationary, enter upon an active phase and bend 

 outwards until their terminally-placed stigmatic tissue, which, meantime, has be- 

 come mature, rests over the nectaries. In this position the stigmas are certain to 



Fig. 300. Autogamy in the flowers of the Willow-herb 

 (Epilobium angustijoliu'tri). 



