84 THE AMERICAN BOTANIST. 



forms as "double" daisies, sunflowers, dahlias, and the 

 like. To these variations in the general form and arrange- 

 ment of the florets must be added the differences that exist ir; 

 the manner of producing seeds. In some the outer circle — the 

 ray flowers — are the only ones that are fertile, in others only 

 the disk flowers bear seeds, while in still others both ray and 

 disk flowers participate in seed bearing. Normally the disk 

 flowers bear both stamens and carpels, but either set may be 

 missing and the same is true of the ray flowers. Another cur- 

 ious thing is connected with their colors. As everybody 

 knows, certain genera may run to yellow-flowered forms and 

 others to blue pink or purple but a single genus rarely contains 

 species with flowers of both colors. In the genera with yello\v 

 flowers albinos are rare — who ever saw a white dandelion, or 

 sunflower? — but in the blue and red flowered genera albinos 

 are common. As might be inferred from their structure, the 

 greatest amount of variation, aside from such qualities as 

 height, hairiness, and leaf forms, is to be found in those flower 

 heads that possess both ray and disk flowers. Here variation 

 may be manifested in the number of rays or in their shape. 

 Quilled forms which after all are possibly reversions to the 

 original form of the flower, are common and when the rays are 

 flat there is often a great difference in their width. Fascia- 

 tions of various kinds also occur. One has only to search the 

 nearest field of daisies, black-eyed Susans, or any abundant 

 composite to discover many of these variations for himself. 



The Struggle for Existence. — The results of Dar- 

 win's remarkable work are so widely known that practically 

 everybody has at least a theoretical knowledge of the struggle 

 for existence, but few really realize how important a factor 

 this is in the life history of a given plant. Recently the writer 

 was impressed with this when examining an especially florifer- 

 ous species of mullein of European origin known as Vcrhas- 

 cum pannosum. A careful count of an average flower spike 



