SPRING FLOWERS 155 



be floating in the air around a colony of the plants. Some of these 

 may come in contact with the stigmas of other flowers, and we can 

 now appreciate the use of the large rough stigmas, which are well 

 fitted to catch and retain the pollen grains borne against them. 



The likelihood of pollination being effected in this way is in- 

 creased by the social mode of growth of the Woodrush, which 

 leads to many inflorescences being present within a limited radius. 

 Some of these inflorescences will bear flowers in the earlier, some 

 in the later stage. This is important, since, as has been seen, the 

 stigma alone is exposed in the earlier stage, and withers before the 

 stamens of the same flower shed their pollen. Self-pollination is 

 thus impossible, and pollen must always be brought from a dis- 

 tinct flower in the second stage, and probably from another plant. 



The Woodrush is an instructive example of a wind-pollinated 

 flower, and its features should be contrasted with those of the 

 insect-pollinated Tulip, in which the general 

 plan of construction of the flower is almost 

 the same. The Woodrush is peculiar both 

 in the absence of conspicuousness and other 

 attractions, which are present in order to 

 attract insect visitors in other flowers, and FlG - 75- Fruit of the 

 in such features as the large stigma and the 

 powdery pollen which directly assist in wind- the seeds. 

 pollination. These general characters are 

 found in the flowers of many other wind-pollinated plants, and 

 associated with them we often find arrangements to prevent self- 

 pollination. This is sometimes effected by the stamens being in 

 one kind of flower and the pistil in another, but in the Woodrush the 

 flower contains both stamens and pistil. We have seen, however, 

 that the sharply marked stages of flowering result in each flower 

 being at first in a pollen-receiving and later in a pollen-shedding 

 condition. It is instructive to compare, in this respect, the Wood- 

 rush with the Ribwort Plantain, which is described below. 



That the mode of pollination is thoroughly effective is shown 

 by the way in which practically every flower gives rise to a fruit. 

 This is formed from the ovary, and when ripe its dry wall splits 

 into three valves which bend apart and allow the three, relatively 

 large, seeds to escape (Fig. 75). 



