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ERIOCAULON DECANGULARE L.; AN ANATOMICAL 
o2 UD 
THEO. HOLM. 
(WITH FIVE FIGURES ) 
In a paper entitled ‘Structure de la racine et disposition des 
radicelles dans les Centrolepidées, Eriocaulées, Joncées, Maya- 
cées, et Xyridées,”* Van Tieghem arrives at the conclusion that 
these orders possess the same peculiarity in regard to the struc- 
ture of pericambium as do the Graminee and Cyperacee, and 
in this they appear to differ from the other orders of monocoty- 
ledons. His conclusions in regard to the Graminez and Cyper- 
acez, however, are mostly based on the observations of Johannes 
Klinge, which are recorded in his excellent work, ‘‘ Vergleichend 
histologische Untersuchung der Gramineen- und Cyperaceen- © 
Wurzeln.”’? It is the structure of the pericambium, Van Tieghem’s 
péricycle, which exhibits such marked variation as to seem charac- 
teristic of certain orders, at least in some of the species, and the 
variation consists in its continuity or interruption by the proto- 
hadrome vessels. Some very instructive tables are contained in 
Klinge’s paper, in which the position of these vesse!s has been 
given in relation to the pericambium of a number of species of 
Graminez and Cyperacee. From these tables it is seen that in 
some species all the proto-hadrome vessels are within the peri- 
cambium, in others only half of them or only a few, while in still 
others they are all in direct contact with the endodermis, having 
thus broken through the pericambium. Van Tieghem describes 
the same variation in Eriocaulacee, etc. Representatives of no 
less than seven orders of monocotyledons thus exhibit this pecu- 
liar structire. 
The continuity of the pericambial stratum is considered 
* Jour. de Botanique 1: 305. 1887. 
* Mém. de l’Acad. Imp. d. sc. d. St. Petersbourg VII. 26:12. 1879. 
Igor] 17 
