110 Botanisches Centralblatt. — Beiheft 2. 



Taxono mic significance of tlie double parenchyma- 



sheath. 



So far as known this new anatomical character occurs only 

 in the family of the Gramineae. The vastness of this family may 

 be realized from the fact that so extremely conservative an author 

 as Bentham estimates the number of species to be about 3,200. 

 Their distinction into tribes and genera is well known to be diffi- 

 cult under the guidance of morphological characters alone, and 

 some recent botanists*) have already demonstrated the import- 

 ance of the anatomical method as likely to lead to a better 

 systematization of the family, Hence the discovery of any new 

 anatomical character like this of the double parenchyma-sheath is of 

 promise Irom the point of view of the systematist. 



With this in mind the writer in choosing species for ana- 

 tomical investigation purposely selected species representing diffe- 

 rent subgenera or sections of the genus; with this result that the 

 new character is found to occur in certain sections and not in 

 others of the genus Aristida as generally accepted at present. 

 Let US therefore look into the history of Aristida as variously 

 delimited by different agrostologists of the past and present. 



Linnaeus**) founded the genus on the following species: 

 Adscensionis and americana, while nearly thirty species were 

 recognized at the time of Beauvais. ***). This author refered 

 the species to four genera: Aristida^ Curtopogon, Chaetaria and 

 ArtJu-atherum^ and a true Aristida was with Beauvais A. lanata 

 Forskaal, which he characterized as possessing: „une veritable 



*) Duval-Jouve (1. c). 



Same: Etüde anatomique de quelques Graminees et en particulier des 

 Agropyrum de FHerault. (Mem. de l'Acad. d. sc. et lettr. de ^Montpellier. 

 Paris 1870.) 



Güntz, H. E., Untersuchungen über die anatomische Struktur der 

 G ramine en-Bllitter in ihrem Verhältniss zu Standort und Klima, [Inaugural- 

 Dissertation.] Leipzig 1886. 



Guerin, P., Sur le developpement du tegument seminal et du peri- 

 carpe des Graminees. [Th^se.] Paris 1899. 



Hackel, Edw., Monographia i^es/wcarMwi Eui-opaearum. 188*2. 



Same, Andropogoneae in A and C. De Candolle's Monographia 

 phanerog. prodomus. Vol. VI. 1889. 



Holm, Theo., A study of some anatomical characters of North Ameri- 

 can Gramineae. I— VII. (Bot. Gazette. 1891. p. 166, p. 219 and p. 275; 

 189l', p 358; 18,t5, p. ?62; 1896, p. Sf)? «nd p. 404.) 



Lund Samsöe, Vejledning til at kjende Graesser i blomsterlös Til- 

 stand (Dnnsk Frökontrol. Kjöbenhavn 1882.) 



Pammel, L. H, The histology of the caryopsis and endosperm of 

 some Grasses. (Contribution from the Shaw shool of Botany. No. 12. 

 St. Louis 1898.) 



Sirrine, E. and Pammel, E., Some anatomical studies of the leaves 

 of Sporobolus and Panicum. (Contribution Bot. Dept. Jowa College No. 1. 

 Des Moines 1><96.) 



**) Linnaeus, C., Species plantarum. Ed sec. Vol, I. Stockholm 

 1762 p 121. 



***) Beauvais, Palisot de: Essai d'une nouvelle Agrostographie ou 

 nouveaux genres des Graminees. Paris 1812. p. 30 etc. 



