T. Holm — Studies in the Cyperacew. 1Y5 



but without developing as a continuous ring outside or between 

 these bundles. 



In proceeding to examine the assimilating tissue of the 

 stem, we notice in Lipocarpha a structure which is very dif- 

 ferent from that of other genera, discussed in our former 

 papers : Carex, Dulichium, Fuirena, Dichromena and 

 Scleria* This divergence consists in the very regular arrange- 

 ment of the palisade-cells radially around the peripherical 

 mestome-bundles. In the other genera, previously described, 

 the palisade-cells were not arranged radially in proportion to 

 the mestome-bundles, but in proportion to the cross-section of 

 the stem itself. We notice, therefore, in Lipocarpha that each 

 of the outer mestome-bundles is surrounded by a closed sheath 

 of palisade-cells, all of which contain an abundance of chloro- 

 phyll-grains. A similar sheath of palisade-cells is, also, 

 observed on the leptome-side of the inner mestome-bundles, 

 adjoining the arch-shaped group of stereome on the hadrome- 

 side. The inner mestome-bundles are, hence, surrounded 

 partly by palisade-cells and stereome. In no other part of the 

 stem is palisade-parenchyma observable, as the spaces between 

 the outer mestome-bundles are occupied by the several layers 

 of epidermis. 



While this singular arrangement of the palisade-cells in the 

 stem of Lipocarpha seems to offer an excellent character by 

 itself, it is, nevertheless, invariably followed by another and 

 still more remarkable feature, represented by the structure of 

 the mestome-bundles. We have already mentioned that the 

 stem possesses two distinct, concentric bands of mestome- 

 bundles, an outer and an inner. The majority of the mestome- 

 bundles are situated in the peripherical band and represent two 

 forms : small and in transverse section orbicular, and larger 

 which are oval in cross-section. The orbicular are the most 

 abundant, but they do not all possess a leptome and hadrome 

 developed to the same extent as the larger, the oval bundles, 

 nor are they all supported by subepidermal stereome, as these 

 invariably are. Those of the inner band are all large and show 

 a very pronounced oval outline ; besides this, they are only sup- 

 ported by stereome on their hadrome-side. But all these 

 mestome-bundles, the large and the small, show the presence 

 of a typical mestome-sheath, the cells of which are but slightly 

 thickened in those species which we have had an opportunity 

 to examine. Inside the mestome-sheath is still another sheath, 

 the cells of which are conspicuously larger than those of the 

 mestome-sheath, very thin-walled and tilled with chlorophyll. 

 However the chlorophyll in this sheath differs in a very marked 

 •degree from that of the palisade-tissue by not being differen- 



* This Journal, vols, iii, iv," v and vi. 



