VOL. XI, NO.12.—BOTANICAL GAZETTE—DEC., 1886. 
The Bulliform or Hygroscopic Cells of Grasses and Sedges compared,” 
W. J. BEAL. 
( WITH PLATE X.) 
As so little attention has been given to this topic, it will be nee- 
essary first to describe briefly the leaf ofa grass. In general, it 
consists of a sheath encircling the stem, and a lamina spreading 
from the upper part of the sheath. The blade is traversed long- 
itudinally by fibro-vascular bundles which vary much in size and 
degree of perfection. In viewing a magnified transverse section 
of a mature leaf of Sesleria (fig. 1), we see: e, an outer envelope 
of cells, the epidermis; 6, the median fibro-vascular bundle; A, A, 
lateral bundles; a, the lower median strand of hypodermail fibers ; 
d, the upper median strand; ¢, d’, the lateral strands. The other 
cells are parenchymatous, most of them containing granules of 
chlorophyll. The vacancy, i, is the lacuna, caused by the rupture 
of some cells. In aquatic grasses the lacune are very large. 
The epidermal system consists of: a, epidermis proper ; f, g, bulli- 
form (blister) cells; ¢, stomata; d, trichomes. 
Of the bulliform cells I speak more particularly. They are 
in longitudinal parallel lines, are larger, extend further into the 
leaf, and have thinner walls than ordinary epidermal cells. They 
are usually more or less wedge-shaped, with the point of the 
wedge towards the outside of the leaf. When dry, these cells 
contract and aid in closing the leaf in two or three ways; when 
moist the leaf expands again. In Zea Mays (fig. 2) these cells are 
raised above the others and puff out like a blister. When viewed 
on the surface of the leaf the bulliform cells are usually seen to 
have the proportions of length and width much like those next 
them. ; 
The number of rows in a species appears to be always uni- 
form, but the number varies with the species from three to twelve 
ina band. If there are many rows the cells are shallow: if few, 
the cells are deep; if three only, those at the side are small, and 
the middle one is very large. ‘I'he arrangement or plan of these 
cells is quite constant in a species, but in a genus they often vary 
widely. : : 
The following examples will give some notion of the variety, 
the sections being made in the widest part of the leaf: 
*Read before the A. A. A. S. Buffalo meeting, 1886. 
