16 UniirrsHi/ of Californiit pHhlicdiions. | botany 



PLANTS RESTRICTED TO THE CANADIAN AND HUDSONIAN ZONES. 



Carex Hallii Poa alpina 



Carex Nebraskensis Ranunculus alismsefolius alismellus 



Montia Chamissonis Silene Parishii 



PinuR flexilis Stellaria ei-ispa 



P. Murniyana Viola blanda 



ALPINE ZONE. 



The most sontlicrii latitude at which the tiora of the Alpine 

 Zone is known to occur in North America is on San Jacinto 

 Mountain, wliere we lind a few characteristic alpine plants 

 growing along the banks of perpetual snow in the cool, shaded 

 canons which descend the north side of the main peak at alti- 

 tudes of between 10, ()()() and 10,800 feet. Since, besides being- 

 very steep, these canons are enclosed by rocky ridges the sides 

 of which are nearly perpendicular, the exact determination of 

 the l)oundaries of this zone was found to be no easy task, and it 

 is not yet known just how far it extends down the north side, 

 l)ut this is probably not more than a few hundred feet. The 

 species restricted to the Alpine Zone are Oxyria digyna, Ranuncu- 

 lus Eschscholtsii , Carex Preslii, and the alpine forms of Spraguea 

 umbellata and Aqnilegia truncata. Growing near these but more 

 common in the lower zones occur Silene Parishii, Draha corrugafa, 

 Heuchera rubescens and a very depauperate form of Holodiscus 

 discolor dumosa. 



The Phytogeographic Formations. 



It is with great reluctance that the term "formation" is used 

 in this pai)er. It has been applied in such various meanings by 

 different botanists that it has become necessary for each author 

 to state his definition of the term in order that intelligibility 

 may be gained. Where here used it has the meaning as 

 originally given to it l)y (Irisebach in 1838.* He looked upon a 

 phytogeographic formation ( pfianzengeographische formation, 

 vegetationsformation) as including "plants which may be very 

 different, l)nt which have properties and characters in common, 

 which may l)e summed up by pointing out several species which 

 exemplify the special characteristics of the whole." 



* A. Grisebach, Ueber den Einfluss des Climas aiif die Bei-jji-onzinif; dev iKit iirlic-lien Floren, 

 Linnffia xii. 160 (1838). 



