4:90 T. Holm — Studies in the Cyperacew. 



The roots have no exoclermis, but the cortex shows three 

 very distinct zones : a peripheral, thin-walled and solid, inside 

 of which are three strata of slightly thick-walled stereome, sur- 

 rounding an inner broad parenchyma of irregularly collapsed 

 cells. Endodermis is moderately thickened all around, and 

 the same structure occurs, also, in the pericambium, which is 

 almost continuous, i. e. only interrupted by two of the twenty- 

 four proto-hadrome vessels. The leptome-strands are distinct, 

 but very narrow. Inside the proto-hadrome are twenty wide 

 scalariform vessels, which surround a broad central mass of 

 thick-walled conjunctive tissue. 



The culm is obtusely triangular, glabrous and hollow ; the 

 cortex represents a very compact parenchyma of roundish 

 cells, but without palisades, and is interrupted by the stereome, 

 which occurs as hypodermal strands bordering on the leptome- 

 side of the mestome-bundles. These are arranged in a single 

 triangular band surrounding a thin-walled pith, of which the cell- 

 walls show very distinct spiral thickenings. 



The leaves are narrow, but flat, scabrous only on the ventral 

 face from minute warts ; the stomata, which are confined to 

 the dorsal face of the blade, are level with epidermis and have 

 a wide but shallow air-chamber. Wide lacunes traverse the 

 chlorenchyma, in this species differentiated as a ventral 

 palisade, and a dorsal pneumatic tissue of irregularly branched 

 cells ; there is, furthermore, a single layer of palisades 

 around each vein, radiating toward the center of these. The 

 stereome is not very thick-walled and occurs as hypodermal 

 strands and bordering on both faces of the veins ; no isolated 

 strand of stereome was observed in the leaf-margin. All the 

 mestome-strands show the usual structure, being collateral 

 and surrounded by a parenchyma- and a mestome-sheath. 

 Although the plant grows in very dry, stony soil, the leaves 

 have no water-storage tissue, but are able to close by means of 

 a longitudinal band of typical bulliform cells, which are 

 located above the midrib, on the ventral face of the blade. 



The anatomy of the Stenocavpoz to which our species belongs 

 has been discussed by the writer in a previously published 

 paper.* When comparing C. petrieosa with these species it 

 will be seen that its root-structure is quite different, since in 

 the other species an exodermis is developed, besides that the 

 peripheral strata of cortex are stereomatic, while in C.petricosa 

 the stereomatic zone is located almost in the middle of the 

 thin-walled cortex. The interruption of the pericambium by 

 the proto-hadrome vessels is, on the other hand, a character 

 that is common to most of these species. 



An obtusely triangular and glabrous culm is seldom met with 

 in this grex but has also been observed in C. ablata. In regard 

 *This Journal, (4), x, p. 278, Oct., 1900. 



