80. GRAMINA. 205 



Lj L. i*'f^ ■ 1333. POA COIVIPEESSA, Li?l?l. 



1334, f. PoA POLTNODA, " Pamr 



Area 1 2 3 4 5 6 7 8 * 10 11 12 13 14 15 * * [18]. 



South limit in Devon, Isle of "Wight, Kent. 



North limit in Fortar, Eclinbm-gh, Lanark. 



Estimate of provinces 15. Estimate of comities 50. 



Latitude 50 — 57. English type of distribution. 



Agi'arian region. Inferagrarian — Midagi-arian zones. 



Descends to the coast level, in the Peninsula. 



Ascends to 100 or 200 yards, iu England. 



Range of mean annual temj)erature 51 — 47. 



Native. Glareal, Eupestral. For the four most north- 

 erly provinces I am aware of only two habitats on record ; 

 namely, " not uncommon " in Forfarshire (Gardiner's 

 Flora), and " common " in Shetland (Edmondston's Flora). 

 As P. compressa attains nearly or quite to a corresponding 

 latitude on the Continent of Em-ope, the Shetland habitat 

 may perhaps be con-ect ; but while the same species re- 

 mains unknown in the wide interspace between Forfar- 

 shire and those boreal isles, there seems sufficient gi-oimd 

 for distrusting the accm-acy of the Author of the Shetland 

 Flora in this instance. Whether P. polynoda be a distinct 

 species from P. compressa, or not, it is impossible at this 

 time to distinguish between theii' localities, so long re- 

 corded under the one name only. And their alleged 

 chai'acters are unsatisfactory. Every botanist who is 

 accustomed to watch the growth of plants, must be aware 

 that the length of internodes, and the distance of the 

 highest knot from the inflorescence, is often much varied 

 according to the humidity of the soil and atmosphere 

 during the period of growth. The difference of 3 or 5 



