T. Holm — Studies in the Cyperacem. 7 



The aerial stem 



which bears the inflorescence is sharply triangular in our 

 species, glabrous or sometimes covered with a few, unicellular 

 hairs along the upper part of the edges, and these are sharply 

 pointed and directed upwards. As in most of the other Cyper- 

 acem with sympodial shoots, the flower-bearing stem is in 

 Scleria preceded by a few leaves, which winter over. 



In its anatomical structure the stem of S. pauciflora shows 

 a distinct cuticle and an epidermis with very thick outer walls. 

 The characteristic siliceous cones which we have mentioned in 

 our previous papers are, also, noticeable in this genus, in those 

 cells of epidermis which lie over the stereome. The bark- 

 parenchyma contains chlorophyll and consists of a compact 

 tissue with several tannin-reservoirs scattered here and there. 

 It is interrupted by the stereome, which covers the leptome- 

 side of the mestome-bundles, reaching through the bark out- 

 wards to the epidermis. "Viewed in transverse section, the 

 stereome is seen to form a large group between the sides of 

 each of the three angles of the stem, while the angle itself is 

 occupied by bark-parenchyma. The mestome-bundles are 

 arranged in two alternating bands, the outer consisting of large 

 and small ones, the inner only of large ones completely im- 

 bedded in the pith, which is solid in this species. A like struc- 

 ture occurs in the lateral peduncles, which, however, are cov- 

 ered by hairs of the same shape which we have described as 

 -characteristic of the main stem. 



The structure of the angle of the main stem seems to offer 

 very good anatomical characters for the species of Scleria, and 

 the following differences have been noticed. In S. pauciflora 

 the angle is occupied by bark-parenchyma, which partly sur- 

 rounds a very small mestome-bundle with little or no support 

 of mechanical tissue on its leptome-side. Inside of the bark 

 follow, then, heavy layers of stereome, which form a solid 

 bridge between the two sides of the angle, and which support 

 a very large mestome-bundle. This same structure is, also, 

 characteristic of S. triglomerata, S. oligantha, jS. Baldwini 

 and S. Elliottii. In S. reticularis, S. Torreyana and S. ciliata, 

 on the other hand, the angle itself is occupied by a small group 

 of stereome which borders inwardly on some strata of bark 

 parenchyma in which a very small mestome-bundle is situated. 

 Next to that occurs a large mass of stereome which connects 

 the two sides of the angle as in S. pauciflora, and which sup- 

 ports a mestome-bundle with a hadrome of considerable devel- 

 opment. S. verticillata, S. hirtella and S. filiformis illustrate 

 a third form of structure, since the angle contains here a 

 single, large mestome-bundle, supported by a strongly devel- 

 oped stereome on the leptome-side. 



