507 
It will be noted that various generalizations upon the zonal 
distribution of plants might be based upon such facts as have been 
given above. Indeed it would seem that there are two principal 
types of plant arrangement in their habitats. These are: (1) Zonal 
and (2) Azonal. The first is connected either with environmental 
conditions as a principal factor, as in the case of the zonal distri- 
bution upon dome-shaped islands, upon voches moutonées, and 
on a larger scale upon mountain peaks and isolated ranges, along 
lake or ocean strand, and surrounding moors, or it may depend 
more particularly upon the character and habits of life of the 
plants themselves, as, for instance, in the care of the “ fairy-ring” 
fungus. The matter may be summed up in a sentence. Gener- 
ally when there is well-marked radial symmetry in the topographic 
Seature “upon which a group of plants is distributed zonal arrangement 
1s the response of the plant population to these symmetrical physto- 
Snomuc conditions ; but when the topographic feature 1s devoid of such 
well-marked radial symmetry the plants dispose themselves according 
to the azonal type. Talus-heaps, flat extended meadows, highly ir- 
regular hills, shallow marshy ponds and other such localities may 
Serve as illustrations of asymmetrical habitats. A variety of con- 
ditions determine whether the distribution upon a given area be 
zonal or azonal. And it is worthy of note that the same for- 
mation may in one case arise by zonal, in another by azonal dis- 
tribution. This was brought out in the discussion of circular solid 
tamarack formations upon a previous page. 
The contemplation of vegetation in any region with these 
Principles in view is certainly illuminating. Practically. it connects 
at once ecologic distribution with physiography, and enlarges the 
content both of topography and of botany. 
Description of Plates. 
Plate 279. Muskeag near Grand Rapids, Minn., showing the pine-covered ridge 
in background, and zones of tamarack, black spruce and Ledum in the foreground- 
Plate 280, Muskeag near Grand Rapids, Minn., showing spruce zone against 
the tamarack, and a central moor with Eriophorum. Looking northwest. : 
Plate 281, Same muskeag as in Plate 280. On the left tamarack faces the moor ; 
on the left the black spruce formation intervenes. The vegetation in the foreground 
is Andromeda, Eriophorum, Carex and sphagnum. 
Plates all from photographs obtained for the author by Director W. W. Pender- 
gast, of the Grand Rapids Experimental Sub-station, 1896. 
