ENGELMANN—NORTH AM. SPECIES OF JUNCUS. 433 
What constitutes a species.—The specific character lies not 
in any single organ of the plant, however essential it may be ; 
only sufficient and corresponding differences in a series of 
organs can authorize us to recognize specific distinction. 
But as such discrimination is of course left to individual 
judgment, different investigators will arrive at different con- 
clusions. Some species, to be sure, vary very little, and will, 
by every botanist, be recognized as distinct from all others, 
and as indivisible; such are, e. g., J. filiformis, J. militaris, 
J. stygius, J. repens ; but other species exercise the botanists 
considerably, some forms being held distinct by some, while 
they are united by others; such are among our species, 
especially J. paillescens, J. scirpoides, J. nodosus, and J. 
Canadensis, all belonging to the group Articulati. I have 
no doubt that some botanists, especially such as have not the 
means of comparing the bewildering quantity of transition 
forms now before me, will find my views in this respect too 
contracted, but careful investigation in the field will, I trust, 
bear me out. 
After these preliminary remarks I submit a list of our 
North American Junci and their principal varieties, as [ 
understand them, followed by an account of their geographi- 
cal distribution. 
Systematic Arrangement. 
GENUS JUNCUS, Lin. 
Sus-Genus I. JUNCUS. 
I, Juncr cenvint, caule aphyllo basi vaginis aphyllis seu rarius fo- 
lia ipso cauli similia gerentibus stipato. 
A. Glomeruliflori. 
1. J. acutus, Lin., California, New Jersey. (?) 
2. J. Remerianus, Scheele (J. maritimus, Auct. Am.), New 
Jersey to Texas. 
FUL LUyY 
B. Singuliflori. 
a. Pluriflori, panicula plus minus composita. 
a. Robustiores, capsulis ovatis seu ob- 
ovatis. 
l. Foliiferi. 
3. J. compressus, H. B. K., California, Mexico. 
2. Aphylli. 
* Hexandri. 
J. Breweri, n. sp., California. 
J. Balticus, Dethard. 
B. littoralis, coast of New England to the Mississippi. 
y- montanus, Western deserts and Rocky Mountains. 
Sub-species J. Pacificus, Pacific coast. 
4. 
5. 
*souUnMIMOY 
