102 Botanisches Centralblatt. — Beiheft 2. 



and thereby easily distinguished froui tlie surroundiiig parenchyma- 

 sheatli, altbough some cases are known where the mestome - paren- 

 chyma itself attains a development like that of a true mestome-sheath 

 (1. c.) In such cases the treatment of the sections with concentrated 

 sulphuric acid and a very careful comparison of the large and 

 small mestome-bundles is necessary for deciding whether such sheaths 

 really represent a mestome-sheath or only a layer of mestome- 

 parenchyma. Hab erlandt's chlorophyll-bearing sheath is a third 

 form of sheath, which so far has only been observed in some 

 genera and species of Cyperaceae in accordance with the obser- 

 vations of Rikli*) and the writer. **) This inner chlorophyll- 

 bearing sheath is always located inside the mestome-sheath, whether 

 the outermost parenchyma-sheath is present or not, and its green 

 cell-content and mostly thin cell-walls make it readily distinguish- 

 able from any form of true mestome- sheaths. 



Over and above these distinct sheaths thus named and briefly 

 characterized, and which are more or less familiarly known to 

 plant-anatomists, there exists, as the researches, the results of which 

 are herein given to the public, prove, that which may be called 

 a second or a double-parenchyma- sheath. 



While engaged in an anatomical study of a collection of plants 

 made by the writer during the summers of 1896 and 1899 in Colorado 

 we noticed among the Gramineae from the plains, that Aristida 

 fasciculata exhibited distinctly a double parenchyma-sheath. Being 

 unable to find any record of this sheath, we submitted our obser- 

 vations to Professor Schwendener, who courteously informed 

 US, that in spite of the large number of Gramineae, which he 

 had examined, he had never observed any instance of such a 

 structure, We did not, however, deem it advisable to publish 

 our observations upon this individual instance, but thought that 

 the same structural peculiarity might perhaps be shared by some 

 of the other Gramineae from the plains or at least by other 

 members of the genus. Therefore we have extended our research 

 to as many species of Aristida as were available, and we have 

 not omitted to consider allied genera, besides a number of other 

 Gramineae, which to a more or less extent, are associated with 

 the various species of Aristida : occupying the same soil and living 

 under the same climatological conditions. The final result of our 

 investigation is, however, that the structural peculiarity which we 

 observed in Aristida fasciculata and which consists of the presence 

 of a double parenchyma-sheath around the mestome-bundles is 

 only possessed by certain species of this genus, not by all, and 

 not by any of the other genera of grasses examined. 



*) Rikli, M., Beiträge zur vergleichenden Anatomie der Cyperaceen mit 

 besonderer Berücksichtigung der inneren Parenchymscheide. [Inaug-Diaser- 

 tation.] Berlin 1«95. 



**) Holm, Theo., The genus Lipocarpha R. Br. (American Journ. of 

 Sc. VII, 1899. p. 171) and Fimbristylii)Ya.hl ; an anatomical treatise of North 

 American species. (Ibidem. VII. p. 435). 



