LESSONS IN BOTANY. 247 



to the stigmatic surfaces by the wind, by insects, or in rare cases 

 by birds. 



The grasses, sedges, pines, oaks and others, having small 

 uncolored flowers, produce great quantities of pollen. As this 

 floats easily in the air it is widely distributed by the wind, so that 

 while there may be instances of self-fertilization, cross-fertiliza- 

 tion is the rule. Other plants have highly colored flowers pro- 

 ducing nectar, which attracts such insects as bees, butterflies, 

 etc. The insects, in their excursions from flower to flower, carry 

 pollen from one blossom to the stigma of another. And this is 

 by no means a matter of accident or chance; in many cases the 

 flower and insect are so adapted to each other that only a par- 

 ticular insect can get nectar from a particular flower, and aid in 

 its fertilization. One case of many maybe mentioned; the yucca 

 in southern climates, ripens its seeds regularly, but while it thrives 

 well in the north it does not mature seed. In the south a little 

 moth called the yuccasella gathers up masses of yucca pollen, 

 and laying its eggs in them thrusts them down a stigmatic tube 

 and thus fertilization is accomplished. The yuccasella cannot or 

 does not live in the north and the yucca ripens no seed in that 

 region. 



It is said that cats saved the clover crop in a certain district 

 in Australia. The cats caught the mice that destroyed the nests 

 of a long-billed bumble bee, which was the principal agent in the 

 fertilization of the clover blossoms. The orchids with their beau- 

 tiful flowers of grotesque forms afford many interesting illustra- 

 tions of mutual adaptation and dependence between flowers and 

 insects. 



The flowers are fertilized, the seeds have ripened and are ready 

 for the soil; if they fall near the parent plant only one or two 

 could find room for growth, so that it seems necessary for seeds 

 to be scattered widely. This is accomplished in various ways; 

 the seeds of the maple and elm are furnished with wings, those of 

 the thistle, dandelion and milk-weed with plumes so that they 

 may be dispersed by the wind. The seeds of many plants are 

 furnished with hooks by which they may become attached to 



