IO 
Plowman. — The Comparative Anatomy and 
3. Peridesm more or less massed centripetally. 
a. Rhizome tuberous, or the internodes very short. 
aa. Endodermis not reinforced. 
aaa. Cortex very aerenchymatous ..... Psilocarya . 
bbh. Cortex compact or sclerotic ..... Cyperus. 
bb. Endodermis reinforced by sclerotic zone . . . Fuirena. 
b. Rhizome elongated, not tuberous. 
aa. Medulla sclerotic ....... Rhynchospora. 
bb. Medulla not sclerotic. 
aaa. Xylem elements few. 
aaaa. Peridesm slightly developed . . Eriophorum (in part). 
bbbb. Peridesm very strongly developed in four or five 
central bundles . . E. Scheuchzeri, E. alpinum. 
cccc. Peridesm well developed in all of the central 
bundles ........ Dichromena. 
bbb. Xylem elements many. 
aaaa. Peridesm slightly developed .... Fimbristylis. 
bbbb. Peridesm very largely developed in all central 
bundles Scirpus (chiefly). 
TABLE I. Rhizome Characters. (Explanation.) 
The symbols + and — , when standing alone or before another descriptive 
symbol, have a numerical significance, as ‘ many ’ or £ few/ When they follow 
another symbol they have a purely qualifying meaning, signifying that the preceding 
character is either well developed or the contrary. The qualifying symbol is doubled 
for emphasis. 
1. Class: A, Amphivasae ; or C, Centrivasae. 
2. Form : t, tuberous ; s, with short internodes ; or 1 , with long internodes. 
3. Central cylinder : c, compact or small ; 1 , loose or large. 
4. Endodermis : +, reinforced ; — , simple ; or 0, undifferentiated. 
5. Medulla : a, aerenchymatous ; c, compact ; or s, sclerotic. 
6. Bundles : s, scattered ; or c, crowded. 
7. Xylem elements : 1 , large ; s, small ; +, many ; or few. 
8. Peridesm : =, uniform ; c, centripetal ; or 0, undifferentiated. 
9. Cortex : a, aerenchymatous ; c, compact ; or s, sclerotic. 
10. Hypoderm : s, complete sheath ; or r, ribs. 
1 1. Tannin : +, much ; — . little ; or 0, absent. 
12. Starch : + , much ; — , little ; or 0, absent. 
The Aerial Stem. 
The aerial stem or culm of the Cyperaceae presents a considerable 
variety of forms. In Cyperus and Eleocharis it assumes practically 
a scapose habit, with a few small or moderately large leaves clustered 
at its base, and terminated above by the simple or compound inflorescence, 
