FLORA OF THE DISTRICT OF COLUMBIA. 



293 



50. CENTAUREA L. 



Besides the species entered below, each of the following, all natives of Europe, has 

 been collected once in oiu* region: Qntaitrea solstitialis L., Vienna, July, 1909 (C. L. 

 Shear); C. vochinensis Bernh., along the Pennsylvania Railroad, southeast of the H 

 Street Bridge, 1915 (/. B. S. Norton); C. nigra L., Daniels Road, July, 1914 (Steele); 

 Cjacea L., Franklin Park and Pinehurst. None of them, probably, is established. 



Bracts ending in long stout spines; heads sessile; leaves with spiny lobes and teeth. 



1. C. calcitrapa. 

 Bracts not spiny; heads stalked; leaves not spiny. 



Stem leaves all diAdded into linear lobes 2. C. maculosa. 



Stem leaves all or mostly entire 3. C. cyanus. 



1. Centaurea calcitrapa L. Star thistle. 

 Abundant in waste ground at Alexandria; occasional about Washington. May- 



Sept. Native of Eur.; adventive in the eastern U. S. 



2. Centaurea maculosa Lam. 



Collected near Mullikin and at Franklin Park; perhaps not established. July-Aug. 

 Native of Eur. ; occasionally adventive in the eastern U.S. 



3. Centaurea cyanus L. Corn-flower. 

 Occasional in waste ground and grain fields. Native of Eur.; often cultivated for its 



showy blue, pink, or white flowers. 

 Known also as bluebottle and bachelor's-button. 



SUMMARY OF THE LARGER GROUPS, WITH NUMBERS OF GENERA 



AND SPECIES. 



PTERIDOPHYTA. 



Ophioglossaceae 



Osmundaceae 



Schizaeaceae 



Polypodiaceae 



Equisetaceae 



Lycopodiaceae 



Selaginellaceae 



Isoetaceae 



GYMNOSPERM AE . 



Pinaceae 



MONOCOTYLEDONEAE 



Typliaceae 



Sparganiaceae 



Potamogetonaceae 



Naiadaceae 



Alismaceae 



Vallisneriaceae 



Poaceae 



Cyperaceae 



Araceae 



Lemnaceae 



X>Tidaceae 



Eriocaulaceae 



Commelinaceae 



Pontederiaceae 



Juncaceae 



MONOCOTYLEDONEAE — Con 



Molantliiaceae 



Liliaceae 



Convallariaceae 



Smilacaceae 



Amaryllidaceae 



Dioscoreaceae 



Iridaceae 



Orchidaceae 



DICOTYLEDONEAE . 



Saururaceae 



^alicaceae 



Myricaceae 



Juglandaceae 



Betulaceae 



Fagaceae 



Ulmaceae 



Moraceae 



Urticaceae 



Loranthaceae 



Santalaceae 



Aristolochiaceae 



Polygonaceae 



Chenopodiaceae 



Amaranthaceae 



AUioniaceae 



Phy tolaccaceae 



Aizoaceae 



Portulacaceae 



Genera. 



7 

 7 

 6 

 1 

 1 

 1 

 3 

 16 



Species. 



9 

 15 

 8 

 6 

 1 

 2 

 9 

 31 



1 

 15 

 2 

 7 

 6 

 23 

 5 

 4 

 8 

 1 

 1 

 2 

 28 

 7 

 8 

 1 

 1 

 1 

 3 



