Holm, Some new anatomical characters für certain GramineMe. 117 



Muhlenhergia Schreb. 



The following species have been studied : 



M. diffusa Schreb. (Deciduoiis forests near Brook- 



land, DC), 

 „ distichophylla Knnth (Arizona, at an elevation of 



7,500 ft.), 

 „ glomerata Trin. (Low grounds, Denver, Colorado), 

 „ gracilis Trin. (Dry mountain-slopes near Golden 



City, Colorado, at an elevation of 6,500 ft.), 

 „ gracillima Torr. (Hill-sides, New -Mexico, at an 



elevation of 7,500 ft.), 

 „ mexicana Trin. (Deciduoiis forests in Brook- 



land, DC), 

 „ soholifera Trin. (Deciduous forests in Brook- 



land, DC), 

 „ sylvatica T. et G. (Deciduous forests in Brook- 



land DC), 

 „ Willdenovii Trin. (Woods, Kentucky). 



The genus is, as already stated, a member of the Stipeae 

 and is, thus, related to Aristida, but it contains only a few species, 

 that are associated with this genus. The species are mostly wood- 

 land-plants or inhabitants of dry mountain-slopes, and vary very 

 much in habit; some are decumbent and profusely branched with 

 numerous lateral inflorescences (M. diffusa, mexicaiia etc.), others 

 are rigid and erect with a single, terminal panicle {M. graciliSy 

 gracillima)^ thus we meet here with the same diversity in habit 

 as we observed in Aristida, for example when we compare A. 

 dichotoma with Ä. stricta or A. lanata. Furthermore the structure 

 of the spikelets, and especially of the empty glumes, i enders 

 important characters for the distinction of the species and was 

 formerly in connection with the habitual differences used for the 

 establishment of independent genera, thus M. diffusa was a true 

 Muhlenhergia with Beauvais, while M. distichophylla was segregated 

 as Fodosaemum; these with other segregates as Vaseya Thurb., 

 Clomena Beauv. , Tosagris Beauv. and Trichochloa Beauv. are 

 now generally refered as mere sections of the genus Muhlenhergia. 



Considered from an anatomical view - point some of these 

 sections appear to possess certain peculiarities, which might prove 

 useful to further studies for the disposal of the species in sections 

 or perhaps subgenera. The material, which the writer examined, 

 contained some apparently very distinct types, yet the number of 

 species was two small for venturing to suggest the reestablishment 

 of some af the older genera of Beauvais for instance. 



By the internal structure ot the leaf the species fall naturally 

 into two groups : the woodland-types, and those which inhabit the 

 dry, rocky mountain-slopes. 



The leaf of the woodland-types is thin, relatively broad and 

 flat, with very shallow furrows on the upper face and scabrous. 



Bd. XL Beiheft 2. Bot. Centralblatt. 1901. 8 



