PROTECTION OF POLLEN. 119 



If the filaments supporting the anthers charged with pollen are sma.l and 

 short, the perianth, which in the inverted flower constitutes their protective cover, 

 is also of small size, as may be seen, for instance, in the case of the Lily of the 

 Valley (Convallaria majalis, cf. fig. 220^). A much longer envelope is assigned, 

 on the other hand, to stamens with long filiform filaments. Flowers of the 

 kind possessing large petals but seldom need to be completely pendulous in 

 order to shelter their pollen, it is usually sufiicient for them to nod, i.e. to droop 

 a little to one side. Thus, for example, the stalks of Lilium candidum bend in 

 the flowering season only just enough to incline the mouths of the flowers in a 

 lateral direction. Usually the form of the protective cover is such that the rain 

 can trickle oflf it in drops. A contrivance far less common is for the petals 

 covering the anthers to form a receptacle out of which the water is periodically 

 emptied. An instance of this is afforded by the South African Sparmannia 

 (Sparmannia Africana). The flower-buds are grouped together in umbels, and 

 are borne on stalks, which are curved in a semicircle outwards and downwards 

 away from the main axis, so that the flowers are inverted and their anthers 

 are turned towards the ground and covered over by the petals. When the flower 

 is open, however, the petals are not simply spread out like an umbrella, but are 

 slightly tilted back, i.e. upwards. The margins of the petals overlap one another, 

 and their outer surfaces, which, in consequence of the inverted position of the 

 flower are uppermost, thus form a basin open to the sky. When it rains this 

 basin placed above the anthers fills with water, thus adding to the weight borne 

 by the stalk, and as drop after drop increases the strain upon the latter a point 

 is at length reached when the basin tips over, letting the water flow over its 

 edge without wetting the cluster of stamens suspended beneath it. This 

 mechanism preserves the pollen clinging to the dehiscent anthers of Sparmannia 

 from rain and dew in spite of their apparent exposure, which to a hasty observer 

 seems to render it inevitable that the stamens should be wetted. 



In some plants whose flowers are arranged in racemes a process of inflection 

 takes place before the floM^ers open, which does not affect the pedicels themselves 

 but the axis from which they spring, the result being that the entire racemes or 

 spikes become pendent. All the flowers are then inverted, and the petals act as a 

 roof in sheltering the pollen adhering to the anthers. This is the case in the Cherry 

 Laurel {Prunus Laurocerasus), the Bird Cherry (Prunus Padus), the Barberr}- 

 (Berheris), and Mahonia. In the Walnut, the Birch, the Hazel, the Alder, and the 

 Poplar {Juglans, Betula, Corylus, Alnus, Populus) also, the rachis of the spike 

 changes its position shortly before the dehiscence of the anthers thus providing 

 a shelter for the pollen as it becomes free. The male flowers of these plants 

 whilst in the bud condition are crowded closely together, and form a stiff' erect 

 cylindrical spike. But before the flowers open the rachis of the spike grows in 

 length slightly and becomes pendent, whilst the flowers it bears are consequent!}' 

 separated a little from one another and become inverted, so that the floral 

 envelopes, which are composed of little scales and perianth-leaves, are uppermost 



