FLOWERS AND THEIR WORK. 



235 



also occur in Lungwort, Bog-bean, Buckwheat, and Flax; 

 these are dimorphic, but some species of Oxalis (Wood 

 Sorrel) are trimorphic like Ly thrum. 



(a) Examine flowering plants in which the staminate and pistillate 

 flowers are distinct and 

 either occur on the same 

 plant, e.g. Hazel, Oak, 

 Pine, Beech, Birch, Dog's 

 Mercury, or on different 

 plants, e.g. Willow, Pop- 

 lar, Red Campion. 



(6) Examine Harebell 

 (or Canterbury-bell) 

 flowers of different ages 

 and note how the broad 

 bases of the stamens cover 

 the honey, how at first 

 the anthers surround the 

 style and shed the pollen 

 on it and then fall out- 

 wards, and how the stig- 

 mas then separate (stage 

 shown in Fig. 82). Make 

 similar observations on 

 the protandrous flowers 

 of Cow Parsnip, Ivy, Willow-herb. 



(c) Examine the flowers of Woodrush, and note the three large 



feathery stigmas which pro- 

 trude from the flower before the 

 stamens come out. Note the 

 scaly perianth ; the flowers are 

 wind-pollinated. 



(d) Make careful observations 

 on the life-history of a Plantain 

 spike (Fig. 83). When the sta- 

 mens of the lower (older) flowers 

 hang out, after the withering of 

 the stigmas, the stamens of the 

 upper (younger) flowers are still 

 in the bottom of the corolla-tube, 

 arid the stigmas projecting out- 

 wards and ready for pollination. 

 Some species have brightly- 

 coloured anthers, and are slightly 

 scented ; these are sometimes 

 visited by insects for pollen. 

 Otherwise the Plantains are wind-pollinated. 



EMBRYO 



Fig. 82. Campanula. 



A, Vertical Section of Flower ; B, Fruit ; C, Longi- 

 tudinal Section of Seed. 



STIGMA 



BRACT 



Fig. 83. 

 A, Spike ; B, Flower of Plantain. 



