ENGELMANN — NORTH AM. SPECIES OP 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. jiliformis, 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. pallescens, J. scirpoides, J. nodosus, and J. 

 Canadensis, all belonging to the group Articidati. 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 I 

 understand them, followed by an account of their geographi- 

 cal distribution. 



Systematic Arrangement. 



GENUS JUNCUS, Lin. 



Sub-Genus I. JUNCUS. 



I, Junci genuini, eaule aphyllo basi vaginis aphyllis seu rarius fo- 

 lia ipso cauli similia gerentibus stipato. 



A. Glomeruliflori. 



1. J. acutus, Lin., California, New Jersey. (?) \ g 



2. J. RcemerianuSf Scheele (J. maritiinus, Auct. Am.), New > 3- 



Jersey to Texas. \ 3" 



B. Singulifiori. 



a. Pluriflori, panicula plus minus composita. 

 a. Robustiores, capsulis ovatis seu ob- 

 ovatis. 



1. Foliiferi. 



3. J. compressus, H. B. K., California, Mexico. 



2. Aphylli. 



* Hexandri. 



4. J. Breweri, n. sp., California. 



5. J. Balticus, Dethard. 



fi. littoralis, coast of New England to the Mississippi. 

 y. montanus, Western deserts and Rocky Mountains. 

 Sub-species J. Pacijicus, Pacific coast. 



