20 HOW PLANTS EMPLOY INSECTS TO WORK FOE THEM. 



tree with pistil-bearing catkins, some of this pollen is rubbed upon the stigmas, 

 and in consequence its fruit may set and the seeds be perfected. The stamens and 

 pistils of Willows being on different trees, and the two sorts of trees very likely 

 at a wide distance apart, it is necessary that the pollen should be carried by insects 

 or some other conveyance, if the Willow is to be propagated by seed. 



35. It might have been left to the winds to waft the pollen. It is so in Pine- 

 trees, Spruces, and the like. But considering what enormous superabundance of 

 pollen these trees produce (even when the two sorts of flowers are on the same 

 tree) in order to make sure of the result, one cannot doubt that there is great 

 economy in the arrangement by which the busy bees are called upon to do the carry- 

 ing. In such instances the insects are probably as useful to the flowers as the 

 flowers are to the insects. 



36. Why should perfect Flowers need to attract Insects? Far the larger number of 



flowers are perfect, that is, are furnished with both stamens and pistils : the sta- 

 mens are almost always more numerous than the pistils, and encompass them ; 

 and each anther contains a thousand or many thousand times more grains of pol- 

 len than there are of seeds to be fertilized, and all so near or in such position 

 that it appears as if the pollen, or a sufficient quantity of it for the purpose, 

 must needs be shed upon the stigmas, either with or without the aid of the wind. 

 Yet here insects, in searching the blossoms for food, might be helpful even if not 

 needful. 



37. There are plenty of flowers, however, to which insects could seemingly be 

 of no use. They have stamens and pistils not only close together, but even in 

 contact, — shut up together in some cases, so that some of the pollen cannot fail 

 to be shed upon the stigma. Pea-blossoms, and those of most of the Pulse Fam- 

 ily are examples of this, having ten anthers closely surrounding one stigma, and 

 enclosed by a pair of the petals. And in the Showy Dicentra (or Bleeding-heart, 

 as it is popularly called, from the shape and color of the corolla), as in all the 

 rest of the Fumitory Family, six anthers are completely enclosed with one stigma, 

 ^hrefe on one side and three on the other, in a cavity just large enough to hold 

 'theni; This cavity is formed by the spoon-shaped summits of the two inner petals, 

 which never separate, being united only at their tips: those of the two outer 

 arid larger petals open and turn back. (See Figs. 9, 10.) One would say that 

 ^uch blossoms are purposely and effectually arranged to be fertilized without any 

 Assistance, and to exclude all interference by insects. Yet they produce nectar 



