﻿432 Nash : The Genera Chloris and 



A Revision of the Genera Chloris and Eustachys in North America. 



By George V. Nash. 



Most 



recent authors have united these two genera, and, while 

 they do bear certain resemblances, we have come to the conclusion, 

 after a careful examination of all the material at our disposal, that 

 they are much better treated as genera than as two sections of one 

 genus. The resemblances are those which are, in great part, com- 

 mon to all the genera of the tribe Chlorideac, that is, they both 

 have one-sided spikes with the spikelets sessile and alternately ar- 

 ranged in two rows. These are their most marked resemblances, 

 and, as intimated above, are not peculiar to either genus. The 

 compressed culms and sheaths are common to both, but much 

 more manifest in Eustachys. The details of the spikelet, however, 

 present differences which seem to justify their separation. The 

 general make-up of the spikelet is essentially the same as it is in all 

 the related genera, but in the forms of some of its parts peculian- 

 ties appear which can be relied upon for generic distinction. It > s 

 true that in a few rare instances in Chloris the awn of the. third 

 scale is very short, but in the great majority of the species the awn 

 is distinctly manifest, and in a large number of them it is very long- 

 In Eustachys, on the contrary, the awn of the third scale is hardly 

 manifest, and usually less than I mm. long, often but a mere point, 

 and frequently entirely wanting. The few short-awned forms of 

 Chloris can be at once distinguished from Eustachys by the second 

 empty scale, which in this latter genus is broad and of approxi- 

 mately the same width from the base to the apex which is at least 

 truncate, and usually 2-toothed or 2-lobed and distinctly awned. 

 In Chloris both the empty scales are lanceolate or narrowly ovate, 

 hence with the sides converging at the acute or acuminate apes, 

 and in a few species the midnerve is continued as a short point- 

 In all the material examined this distinctive character of the sec- 

 ond scale is constant, and this, in the case of Eustachys, in conjunc- 

 tion with the more flattened culms and sheaths and the strongly 

 equitant character of the latter at the base of the culms, together 

 with the absence of the awn in the third scale, or, when present, ifc 



