106 Botauisches Centralblatt. — Beiheft 2. 



Äristida (jracüis Ell. (D. C. Brookland). 



„ Havardii Vas. (Texas : Presidio Co.). 



„ Humboldtiana Trin. (New Mexico : Organ Mts.). 



„ Hystrix L. (East. India). 



„ intermedia Scribn, (Missouri : Biloxi). 



„ Kotschyi Höchst. (Nubia). 



„ Icmata Poir. (Mo: dry Pine-barens). 



„ Meccana Höchst. (Nubia). 



„ mnrina Cavan. (Uruguay: Montevideo). 



„ Nealleyi Vas. (Texas : Presidio Co.). 



„ oligantha Michx. (D. C. : Brookland). 



„ palustris Vas. (Mo. : Biloxi.). 



„ purpurascens Poir. (D. C. Brookland). 



„ jpurpurea Nutt. (Ariz. : Tucson). 



„ ramosissima Engelm. (Mo. : San FranQois Co.). 



„ Reverclionis Vas. (Texas: Presidio Co.) 



„ scabra Kunth {patida Chapm.) (Florida: Titusville). 



„ simpliciflora Chapm. (Florida: Apalachichola). 



„ spiciformis Ell. (Florida: Tampa). 



„ striata Michx. (Florida : Jacksonville). 



„ vagans Cavan. (Australia). 



„ virgata Chapm. (Florida). 

 The majority of these species are inhabitants of dry, sandy 

 or clayish soil on plains and prairies, while some occur also on 

 mountain slopes; only a very few: A, jpalustris and spiciformis 

 were collected in moist ground in pine-barrens. However if we 

 compare the leaf-?tructure of these species with that of A. fasci- 

 culata, it is readily noticed that the arrangement of tbe tissues 

 is exactly the same in all these species; moreover the blade 

 exhibits the same furrowed upper surface and is more or less 

 conduplicate when dry, with power to open, when the atmosphere 

 becomes charged with moisture. — None have broad leaves, and 

 in no instance is the midrib any more prominent than most of 

 the others, neither on the upper or on the lower face, there being 

 no stereome so prominently developed beneath the midrib so as 

 to form a keel and no larger group of bulliform cells above this 

 to distinguish it form any of the others. It would not, however, 

 be difficult to draw up a list of anatomical characters, by which 

 many of these species might be recognized, but as the object of 

 the present study is not to establish an anatomical characterization 

 of the species, we will confine ourselves to a mere general con- 

 sideration of the various modifications, which the leaves exhibit. 

 Beginning with the epidermis, we bave mentioned the deve- 

 lopment of long hairs on the upper surface of A fascicidata, and 

 a similar covering of the blade is also observable in a number 

 of species, while in others the epidermal projections consist merely 

 of short papillae, pointed or nearly obtuse. But there is no 

 evidence this varied covering with hairs or papillae is produced 

 by the nature of the surroundings, hence constituting an ephar- 

 monic character, for we find the long hairs developed on the 



