430 IOWA ACADEMY OF SCIENCE 



Agrostis aequivalvis Picea sitchensis 



Alnus sitchensis Poa leptocoma 



Arnica latifolia Pteridium aquilinum pubescens 



Bromus sitchensis Pyrus diversifolia 



Carex mertensii Romanzoffia sitchensis 



Carex sitchensis Salix sitchensis 



Cassiope mertensiana Saxifraga bongardi 



Cladothamnus pyrolaeflorus Saxifraga mertensiana 



Claytonia asarifolia Scorzonella borealis 



Corallorhiza mertensiana Sorbus sitchensis 



Elymus borealis Trisetum cernuum 



Festuca subulata Tsuga mertensiana 



Juncus mertensiana Valeriana sitchensis 



Lycopodium sitchense Washingtonia purpurea 



LIFE ZONES REPRESENTED. 



There are three of the life zones represented. These are the 

 Canadian, Hndsonian and Arctic-Alpine. Owing to the moist 

 and equable conditions the limits of these zones are not well 

 defined. "While characteristic Canadian species, such as Corn us 

 Canadensis and Sanguisorba latifolia, occur down to the sea 

 level, we find a liberal admixture of species generally classed 

 as Humid Transition. These, indeed, include some of our com- 

 monest species such as Rubus spectabUis and Ecliinopanax hor- 

 ridum. On the other hand, some of the characteristic Hud- 

 sonian plants are also found near sea level and growing freely 

 in company with the Humid Transition and Canadian species. 

 Among these may be mentioned NephropKyllidiwm crista-galli. 

 Even some Arctic-Alpine plants grow freely near sea level and 

 among these may be mentioned Emp( trum mgrwm, which is the 

 most abundant and characteristic of all the higher plants grow- 

 ing on the peat bogs or Muskeg. 



The characteristics of the Arctic-Alpine zone appear at about 

 2.500 feet elevation. Plants properly belonging to the Hud- 

 sonian zone may reach an elevation of nearly 3,000 feet, while 

 the Canadian species may reach 2,000 feet. 



HABITAT GROUPS. 



In considering the ecological aspects of the flora one finds 

 that the plants can be segregated into a number of habitat 

 groups. These are quite well defined, corresponding to their 

 physical environment. Mixtures generally occur only in in- 

 termediate situations. The typical habitats are five, as follows: 

 Littoral, Forest, Muskeg, Aquatic and Alpine. To these might 

 be added a sixth — the weed habitat. These will now be taken 

 up separately. 





