404 THE PAN DAN ALES 



association of numerous hairs with both the stamens and pistils. 

 These organs are supposed to be sterile sporophylls so that we 

 have here a very good illustration of a primitive type of flower. 

 The microspores are carried to the stigmas of the pistils by the 

 wind. 



Such wind pollinated flowers are characterized by several fea- 

 tures well illustrated in the cat-tail. The microspores must be 

 produced in large numbers since the chance of one reaching the 

 stigma of another plant rapidly decreases as the distance tra- 

 versed by the spores increases. This probably accounts for the 

 growth of such plants in dense colonies since the close proximity 

 of the plants greatly increases the chance of the microspores 

 reaching the stigmas. The Finales, grasses, willows, oaks, etc., 

 are other illustrations of a very large series of plants, some 

 10,000 in number, that have a similar habit. Wind pollinated 

 flowers are inconspicuous and simple in structure. You will 

 notice that showy perianths, nectar and perfume glands are 

 developed only in such flowers as utilize insects for the distri- 

 bution of the microspores. The stigmas of these flowers are 

 usually large and hairy or brush-like and conspicuously exposed 

 so as to increase the chances of catching the microspores, thus 

 reducing the dangers of this rather risky method of crossing. 

 You will also observe that wind pollinated flowers are usually 

 characterized by having imperfect flowers, "the stamens and pistils 

 being developed on different parts of the plant, or on different 

 plants. By this arrangement, the advantages of crossing are 

 secured and it also happens that the microspores are either 

 scattered before the stigmas of neighboring flowers are mature, 

 or, more frequently after they have withered and are therefore 

 no longer capable of catching and nourishing the spores. In 

 this way it comes about that the microspores, even when close 

 to the pistillate flowers as in Typha, are often only of service 

 when carried to some earlier flowering plant whose stigmas are 

 mature. In the cat-tail, the microspores are shed a day or so 

 before the stigmas on the same spike are mature and so there 

 must result the benefit that comes from crossing two more or 

 less widely separated plants (page 144). The stamens soon 



