FAMILY VIII, 1S0ETACE/E Underw 
H ERBS, aquatic or in moist ground, with simple, rush-like 
leaves in a rosette, from a fleshy trunk or corm. Leaves 
mostly with breathing pores (stomata) usually quadran- 
gular, containing four vertical air channels divided by frequent 
cross partitions and furnished always with a central vascular bun- 
dle, and sometimes with others on the circumference (peripheral 
bast-bundles ) Sporangia quite large, one-celled, orbicular to ob- 
long, usually thin ; sessile in a cavity M the axils of the leaves, 
more or less covered with a membrane (velum) produced from the 
edges of the cavity ; those of the outer leaves usually containing 
globose macrospores, the inner containing very small, obliquely- 
oblong, three-angled microspores. Macrospores with a white sili- 
cious crust, which is marked by an equatorial line and on the up- 
per surface by three equidistant longitudinal lines meeting at the 
apex of the spore (commissural ridges); silicious integument mark- 
ed between the ridges with spines, tubercles, reticulations, etc. 
which serve in a measure to distinguish the species. Microspores 
white, grayish or light brown ; glabrous, papillose, muriculate or 
spinulose. 
One genus, comprising about fifty recognized species, of which 
eight species and five varieties are known within our limits. 
In the following pages are described several forms in this genus 
which have not previously been noticed, and one of them, I. Eatoni 
previously confounded perhaps with the larger forms of I. Engle- 
manni , has proyed upon examination to be one of the most remark- 
able of the North American species. 
