T. Holm — Studies in the Cyperacece. 



11 



•a, o and c show the incrustations as seen from within the cell 

 with a part of the cell- wall still remaining ; figure d represents 

 •one of the smallest incrustations, seen from above. These 

 silicious incrustations dissolved in a concentrated aqueous solu- 

 tion of potassium in about forty- eight hours. 



Silicious incrustations are also known to occur in the Gram- 

 inece, and Dr. Aug. Grob has lately published a very important 

 treatise of this subject.* He has, however, confined himself 

 to the Graminece, and judging from his descriptions and figures, 

 the incrustations which we have observed in Scleria differ 

 very much from any of those that have been found in the 

 Graminece or other monocotyledonous orders. 



The pericarp of Scleria contains also a vast amount of silica. 

 It lies in two distinct strata of which the outer one is built up 

 by a homogeneous tissue of polyedric cells ; the inner part 

 -consists of a single layer of cells with very long and thin 

 radial walls. It is the outer tissue that undergoes the incrusta- 

 tion, and when macerated the silicified cells form some very 

 beautiful structures like stars, for instance, in S. paicciflora and 

 others. Considered from an anatomical point of view, the 

 North American species of Scleria show several characters in 

 common ; thus it does not seem probable to distinguish all the 

 species by means of their structure alone. We have, never- 

 theless, enumerated the most salient points in the accompany- 

 ing table, from which the anatomical characters may be readily 

 seen, at least in some of our species. 



Leaf. 



Stem. 



S. pauciflora 



S. triglomerata 



S. oligantha 



S. Baldwini 



S. cilia ta. 



S. filiformis 



S. Elliottii 



S. Torreyana _ _ 

 S. reticularis .. 



S. hirtella 



S. verticillata . 



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* Grob, August, Beitrage zur Anatomie der G-ramineeu-blatter, 

 Botanica, Stuttgart, 1896, p. 34. 



Bibliotheca 



