Holm — Studies in the Cyjperacew. 



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composed of equally thickened cells, those on the leptome-side 

 being smaller and with narrower lumen than the others. The 

 mestome-bundles seem to represent three different forms in 

 the leaf of JJichromena, but not so much in regard to the 



development of the leptome and 

 the hadrome as in regard to the 

 difference in their mechanical sup- 

 port. The largest bundles have 

 the leptome and hadrome well 

 developed and not separated from 

 each other by thick-walled mes- 

 tome-parenchyma ; these bundles 

 are supported by large groups of 

 stereomeon both faces, both groups 

 extending from the corresponding 

 epidermis. The mestome-bundles, 

 which may be designated as those 

 of second degree, have, also, a well 

 differentiated leptome and had- 

 rome, besides two groups of stere- 

 ome, but this tissue does not here 

 extend to the epidermis of the 

 lower face. The smallest bundles 

 contain mostly leptome, and their 

 mechanical support consists only 

 of a few stereome-cells on both 

 faces of the bundle, thus interrupt- 

 ing the parenchyma-sheath, but 

 without coming in contact with the 

 epidermis. The general distribu- 

 tion of the stereome has, thus, 

 already been indicated, and it may 

 be added that no isolated groups 

 of this tissue were observed in the leaf of our plant, not even in 

 the margin, where, although present, the stereome was in con- 

 nection with a small mestome-bundle. The leaf of Dichromena 

 shows, therefore, a rather firm structure in regard to the dense 

 mass of mesophyll, which is entirely destitute of any openings 

 large enough to be designated as lacunes. It has, also, been 

 stated that tannin was observed in the epidermis, and quite 

 abundantly in the mesophyll, besides that it was, also, traced 

 in the hadrome of most of the mestome-bundles. 



If we now examine the leaves of the involucre, we find a 

 very singular structure, corresponding to that which Lager- 

 heim (1. c. iv) has observed in D. ciliata Vahl from Ecuador. 

 The discolored part, the base of the involucre, has the epidermis 

 of the upper face developed as a stratum of large papillose 



Fig. 2. Transverse section of 

 a mestome-bundle from the leaf- 

 blade. Ep, the lower epidermis ; 

 S, stereome; PS, parenchyma- 

 sheath; M, mestome-sheath ; T, 

 tannin reservoir, indicated with 

 black in four cells of the section. 

 400 x natural size. 



