68 THE AMERICAN BOTANIST 



nomenon of dimorphism, or two modifications of the flowers 

 of the same species, long observed by botanists and florists, 

 but the significance of which was explained by Darwin, 

 Mueller, Asa Gray and others. The individuals are seen to 

 grow in detached groups or clumps, and if one closely ob- 

 serves these, he will soon note that in one group all the 

 flowers have long projecting stamens and short included styles, 

 while other clusters more or less remote, have the styles project 

 while the stamens are short and included in the tube of the 

 corolla. This is an arrangement to insure cross-pollination, 

 and to bring about perfect results as to vigor and number of 

 offspring. It used to be taken for granted that where stamens 

 and pistils co-existed in the same flower, they necessarily re- 

 acted upon each other. Now it is known that in a vast num- 

 ber of cases there must be an interchange of pollen between 

 distinct individuals, of course of the same species. In the 

 late '60s and early '70s this introduced a most fascinating sub- 

 ject of research, and young botanists especially, were delighted 

 with this work. It is a joy to recall that one fought in the 

 line of the early skirmishers. 



When such flowers are covered by gauze and insect 

 visitors excluded, either no seed is set, or, as a rule, it is less 

 vigorous, of lighter weight, and not so potent as where in- 

 sects have free access to the blossoms. 



In the same fields where innocents abound, one usually 

 observes also a great profusion of "early everlasting" or 

 "ladies-tobacco," a humble composite w'hich shows distinct, 

 separated sexes. The staminate plants can be distinguished 

 even at a long distance by the rusty-red color of the anthers 

 or pollen-cases. The pistillate have abortive or no stamens, 

 filiform-clubshaped stigmas, and very downy abundant pappus, 

 which finally blows loosely over the fields. 



Anyone who even for a few seasons studies the habits 

 of plants, will, among other things learn, that they have their 



