W . 



• a Yol. XIX, pp. 183-192 December 8, 1906 



PROCEEDINGS ' 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



NOTES ON GENERA OF PANICEAE. I. 

 BY AGNES CHASE. 



One of the chief distinguishing characters of this tribe of 

 grasses is the single fruit, composed of the more or less indurated 

 lemma and palea, the latter firmly clasped by the margins of 

 the lemma (rarely loose, as in Leptocoryphium and Hymenachne) , 

 enclosing the free grain. This simple arrangement is variously 

 modified in the different genera. After several years' study of 

 the fruits of this tribe the writer proposes to. offer this and sub- 

 sequent papers on the genera with special reference to the fruits, 

 figuring and describing the fruit of the type species of each genus. 



It may be well to state why the character of the fruit is held 

 to have superior generic value. It is because: 1. 'The character 

 of the fruit is constant in the same species. The first glume 

 may be present or obsolete in PaspahCm* disttdiuni L., P. Drum- 

 mondiiY&sey, P. bifidum (Bertol.) Nash, and in a few others, not 

 only in the same species but in the same specimen, but within 

 are always the same plano-convex, chartaceous-indurated fruits, 

 the lemma with inrolled margins, the palea included at the 

 apex as well as on the margins; Reimaria oligostachya Munro 

 may lack but one instead of both glumes but the fruit remains 

 constant; Echinochloa crus-galli (L.) Beauv. may have very long 

 awns or be mucronate only, but the fruit will have the charac- 

 teristic abruptly acuminate apex, the palea free at the summit. 

 2. The fruit with but slight modifications is constant for greater 

 or smaller groups of similar species; that is, taking the fruit as 

 a generic character it assembles species which show other resem- 

 blances, and does not arbitrarily assemble those which show no 

 close affinity, as does the character of the presence of the first 

 glume in Paspalum, which places in Dimorphostachys, founded 

 on Pmpedmn monostachyum H. B. K., such diverse species as 

 P. Drummondii Vasey and P. Schaffneri Fourn., when both have 



34— Pkoc. Biol. Soc. Wash., Vol. XIX, 1906. (183) 



/ 



