ISO Botanisches Centralblatt. — Beiheft 2. 



Gramineae, Cyperaceae, Juncaceae etc.*), and can ouly be defined 

 in this way ; to consider it as a mestome sheath is at once excluded 

 by the fact that it contains Chlorophyll, furthermore ou account 

 of the shape of the cells. 



These sheaths as they occur together in cur Aristidae may 

 possibly be regarded as an inherited character rather than an 

 epharinonic, since they are equally well developed in species from 

 arid plains, rieh prairies, hill-sides, tields and low pine-barrens, 

 while at the same time they are wanting to many species from 

 alHed and associated genera of the order. 



And we have also shown that it is not a structure that is 

 especially characteristic of Aristidae only from the plains and 

 prairies in this country, but that other members of the same 

 section Cliaetnria from Asia, Africa and Australia exhibit exactly 

 the same peculiarity. — Characteristic of these Aristidae with a 

 double sheath is the absence, and evidently the constant absence, 

 of a mestome-sheath, besides that there is very little thick-walled 

 mestome-parenchyma visible in these species; the plumose-awned 

 Aristidae have no mestome-sheath either, but the mestome-paren- 

 chyma is in these species very prominently thick-walled and occurs 

 often as almost continuous sheaths around the leptome and hadrome, 

 thus simulating a true mestome-sheath, The presence of a mestome- 

 sheath in all the other Gramineae, which we have studied, and 

 which may be added to those, already enumerated by Professor 

 Schwenden er (1. c. p. 413) as possesesing this sheath, seems 

 surely to confirm the statement made by this author (1. c. p. 414) 

 that its development does not depend on the surroundings, climate 

 er soil. Because we found the mestome sheath developed in several 

 genera from the plains, prairies and woodlands, of which many 

 species inhabit very different localities, but in which this parti- 

 cular sheath is, nevertheless, present with no modification what- 

 soever. The constant lacking of this same sheath in Aristida 

 from so man}'- and very remote stations speaks also in favor of this 

 supposition. 



But it woulJ not be natural to divide Aristida or perhaps 

 any other genus simply on account of peculiarities in structure, 

 and we, therefore, do not approve of the Separation of certain 

 genera of Cyperaceae on account of the presence or absence of 

 the green sheath inside the mestome-sheath. We allude to Dr. 

 Rikli's Suggestion (1. c.) that Cyperus for instance must he con- 

 sidered as two distinct genera: Chloro- and F,u-Cyperus in respect 

 to the presence or absence of this inner sheath. Having studied 

 many species of Cyperus from North America and from very 



*) Pde-Laby describes the ordinary parcnchyma-«heath of the Gra- 

 mineae and niakes the following Statements: „La presence de cette gaine 

 verte ou incolore, n'a pas ete signalee, ä ma connaiseance" and „Seh wen- 

 dener est lo soul qui ait fipuree mais il n'en fait pas une mention 



speciale d ins le texte !" — (Etüde anatoiiiique de la feuille des Graminees 

 de la France. (Annales des sc. Botanique. Paris 1898. p. 237 and 238.) 



