THE AMERICAN BOTANIST. 45 



good soil and protected from their enemies do not appreciate 

 it. Of such plants, the butter-fly weed {Asclepias tuberosa) 

 the partridge pea {Cassia chamaecrista) and the Western 

 sunflower (HeliantJius occidentale) may be taken as examples 

 They will grow in good soils, but they are never so showy 

 as when, contending with the inhospitable phases of nature. 

 In good soils they run to leaves. Desert and alpine plants are 

 well-known to have larger flowers in proportion to their size 

 than plants in milder regions and if we are to make them at 

 home in our gardens, we must not favor them too much. 

 They are plants looking for trouble and not quite satisfied 

 unless they find it. 



Pollination of Datura. — The fact is pretty generally 

 accepted that the showy corrollas of flowers have been called 

 into being for the purpose of securing the visits of pollinating 

 insects. Certain it is, that plants without showy flowers are 

 seldom visited by bees and butterflies and few if any wind 

 pollinated flowers are showy. Notwithstanding this, the flow- 

 ers of the common jimson-weed {Datura sfranioniuin) seem 

 to be pollinated before they open and so have no need of open- 

 ing at all. The corolla is in one piece, as in the morning 

 glory but the five petals that compose it are plainly to be traced. 

 In the center of each petal, toward the base, is a long deep 

 well of nectar, and as the flower opens it gives out a strong 

 sweet odor that is unmistakably for the attraction of insects, 

 and yet, if we look at the very instant of its unfolding, we 

 find that the anthers are open and some of the pollen already 

 shed upon the stigma. Unless pollen brought from other 

 flowers is more powerful on the stigma than its own pollen, 

 it is difficult to see how the color, nectar and odor serve the 

 plant. 



