CROSS-POLLINATION IN PRIMULAS 69 



relative position as the head of the style in the first 

 set of flowers. The gi^eat naturalist, Charles Darwin, 

 showed that these differences constitute a special 

 mechanism or contrivance to ensure cross-fertilisation. 

 For example, a bee, visiting a long-stamened flower, 

 would get dusted with pollen around the base of its 

 proboscis or tongue, and this pollen could not fail to 

 be deposited on the stigma of the next long-styled 

 flower it visited. Darwin found by experiment that 

 a full yield of seed is only obtained when the pollen 

 from a flower with long stamens is transferred to the 

 stigma at the top of a long-styled flower, or when the 

 pollen from short stamens is transferred to a flower 

 with a short style. This is '* legitimate pollination." 

 If by any chance illegitimate pollination takes place — 

 that is, from a short stamen to a long style, or vice 

 versa — the seeds that result are few, and more or less 

 sterile. A similar adaptation is met with in other 

 Alpine Primulas, including P, farinom, and also in 

 one of the Androsaces. In some Lowland plants, for 

 example in Lythrum, three kinds of flowers occur with 

 different lengths of stamens and styles. 



The Bird's-eye Primrose, Primula farinosa, Linn. 

 (Plate XIII), is so called because the pale lilac flowers 

 have a yellow " eye " or ring round the throat of the 

 funnel-shaped corolla. This plant is one of the 

 earliest spring blossoms in the damper pasturages, 

 where it flowers in countless millions. The leaves 

 are green and smooth above, but are covered below by 

 a white, mealy wax or bloom. 



