1908] HOLM—SISVYRINCHIUM 185 
is occupied by a pith, which is frequently somewhat thick-walled 
and solid. In the wings the mestome strands are few, and they show 
mostly the same position of the hadrome, which is turned toward 
the center of the stem; it is only the marginal mestome strands that 
differ in this respect, the leptome and hadrome being vertical on the 
surface of the wings, instead of parallel. 
In S. grandiflorum the structure of the stem is somewhat different ; 
the outline is less compressed and there are many deep furrows. 
These furrows contain cortical parenchyma, and the peripheral band 
of small mestome bundles is located in the ridges, thus imbedded in 
the cortex and removed from the stereomatic sheath. The inner 
band of mestome bundles, on the other hand, is located inside the 
stereome, as in the other species described above. 
The structure of the stem is thus very uniform in these species of 
Sisyrinchium, and it seems characteristic of the genus that no hypo- 
dermal mechanical tissue is developed; that there is a strong sheath 
of stereome Separating two concentric bands of mestome bundles, of 
which the peripheral are of the same size and much smaller than the 
inner ones; furthermore, the winged stem of most of these species 
constitutes also a very conspicuous feature. 
LEAVES 
The foreleaves are membranaceous, almost destitute of chloro- 
phyll, and strongly compressed from side to side; they are frequently 
scabrous from thick-walled papillae (fig. 12), but only on the dorsal 
face. The cuticle is smooth, and the epidermis is moderately thick- 
walled on the dorsal face, but thin-walled on the ventral. There is 
oe chlorenchyma in the middle portion of these leaves, and it con- 
“sts of roundish cells throughout, with very little chlorophyll; the 
broad and very thin margins of the foreleaves consist only of epi- 
dermis, that of the dorsal face. The stereome is very poorly repre- 
sented; it occurs as two very small, hypodermal strands, one on each 
Side of the ventral sinus above the midrib, and the veins have a few 
layers of this tissue on the hadrome side. There are several mestome 
Strands in these leaves (3 to 8) and the midrib is usually a little thicker 
than the others; the mestome strands are collateral, and surrounded 
a parenchyma sheaths. While the leptome is well developed in 
