ENGELMANN — NORTH AM. SPECIES OF JUNOUS. 437 



Geographical Distribution. 



Of the fifty species above enumerated, thirty-three, or 

 two-thirds, are peculiar to our country, and seventeen, or 

 one-third, occur also in other parts of the world. Two of 

 these seventeen (J. effusus and bufonius) are cosmopolitan 

 species, which are found almost in all countries of our globe ; 

 six (J. arcticus, trifidus, biglumis, triglumis, stygius, and 

 castaneus) are alpine or arctic forms, which also inhabit 

 appropriate localities in the old world ; three (J. acutus, 

 Balticvs, and Gerardi) grow principally near salt water, 

 and also occur in Europe, and the former, also, in Africa and 

 South America ; three others (J. filiformis, articidatiis, and 

 alpimts) make their home in the northern parts of the north- 

 ern hemisphere ; one (J. tenuis) is also found in middle 

 America and western Europe ; and two extend southward 

 over our limits, J. compressus into Mexico, and J. procerus, 

 if our plant is correctly referred, to Chili. 



The different forms of J. Balticus, nodosus, and Canaden- 

 sis, grow in diflerent regions. The eastern and northern J. 

 Balticus is distinct from the form of the interior plains, 

 and very much so from that of the Pacific coast ; the Texan 

 form of J. nodosus is very different from the northern one, 

 and that of the western States and territories is quite unlike 

 the others ; J. Canadensis has a northern, an eastern, and 

 a third form, which is more generally distributed. 



None of the eight southern species are found anywhere 

 else, and of the nine Pacific species only the two above men- 

 tioned extend beyond our territory to other parts of America, 

 adding another proof of the Avell known fact, that of all our 

 Floras that of the southern and that of the Pacific States are 

 the most peculiar and exclusive ones. 



From their geographical distribution our species may be 

 arranged thus: 



1. Over the whole country grow J. effusus, tenuis, bufoni- 

 us, and nodosus. Of these only the last one does not extend 

 into other Floras. 



2. Over the whole country, with the exception of the 

 western Plains and Mountains and the Pacific slope : J. 

 marginatus and 2^llesce?is, both peculiarly North American. 



3. Over the whole country with the exception of the great 

 interior valley and the Pacific region : J. pelocarpus and 

 Canadensis / both only found in North America. 



4. In the great interior valley from Michigan to the Rio 

 Grande: J . brachycarpus, and, with more extensive limits, 

 one of the forms ofj.nodostis (the var. megacephalus). 



5. Northward — J. filiformis and the northern varieties of 

 J. nodosus and Canadensis ; north-eastward — J. articulatus, 



