COW-PARSNIP 5 



If the inflorescence is now regarded as a whole we shall obtain 

 an explanation of its use in pollination. The flowers are not 

 very large or individually conspicuous, but by being grouped in a 

 compound umbel and all brought to one level they form a con- 

 spicuous white expanse readily seen from a distance. The greater 

 development of the petals of the marginal flowers assists in this. 

 The crowding of the flowers in the young condition lessens the 

 heed of individual protection by means of a calyx, and the sepals 

 are reduced to useless rudiments or are wanting. Even the develop- 

 ment of an investment of protective bracts is very slight in the 

 Cow-Parsnip. The reduction of the calyx and the conspicuous- 

 ness, not of single 

 flowers but of the 

 whole inflores- 

 cence, should be 

 compared with 

 what was seen in 

 such plants as the 

 Dandelion and 



~ . FlG. 2. Flowers of the Cow-Parsnip. A, entire ; B, cut in 



LJaiSy. half lengthwise. (After Baillon.) 



The conspicu- 



ousness of the umbel is of use in attracting insects, which 

 effect the pollination of the flowers. The Cow-Parsnip is 

 visited by a large number of insects of different kinds. There 

 is here no exclusion of the shorter - tongued insects by the 

 nectar being concealed at some depth, since this is secreted by 

 the freely exposed surface of the nectaries in the centre of the 

 flower. The stamens open and shed their pollen before the stigmas 

 are ready to receive pollen, but the stigmas mature rapidly and 

 thus the possibility of the flower being self-pollinated is not 

 excluded. As the insects pass from flower to flower cross- 

 pollination is, however, more likely to take place. In the 

 umbels formed later, while the marginal flowers have stamens 

 and stigmas, the pistil of the central flowers is in a degenerate 

 and useless condition. These flowers are thus practically 

 male flowers, and, while they do not develop fruit, supply 

 pollen which will be carried by insects to the stigmas of other 

 flowers. 



