36 HARPER 



Method of Treatment of Habitat-Groups. 



It has been customary with phytogeographers in discussing a 

 group of plants having the same habitat to treat the component 

 species all alike, arranging them in systematic sequence, or 

 alphabetically, or in no definite order. But this gives no ade- 

 quate idea of their arrangement in nature. In the treatment here 

 adopted I have endeavored by several comparatively simple 

 devices, the application of which will be self-evident after a little 

 explanation, to give the reader (especially if he is acquainted 

 with the species mentioned) as vivid an idea as possible of the 

 actual appearance of each group. 



First of all, the species are separated into four classes, corre- 

 sponding to the four principal strata of vegetation observable in 

 almost any forest, viz., trees, shrubs, vascular herbs, and cellular 

 cryptogams. 1 These are distinguished by their positions with 

 respect to the lateral margins of the page, the names of 

 trees being placed farthest to the left and the others suc- 

 cessively farther to the right. These four groups are not al- 

 ways sharply defined in nature, however, and some exceptions 

 have to be allowed for. For instance, a few species, such as- 

 Magnolia glauca and eight or ten others, are sometimes trees and 

 sometimes shrubs. Again, our two palms, Sabal and Serenoa, 

 are neither trees, shrubs, nor herbs, but I have classed them 

 arbitrarily with the shrubs. And some species which have an 

 evergreen aerial stem and therefore do not come within the strict 

 definition of herbs, such as Mitchella, Opuntia, Smilax pumila, 

 Dendropogon, Selaginella, and Lyco podium, are classed as herbs 

 on account of their size, and lack of genuine woody tissue. 

 Then I have distinguished evergreens by heavy type, 2 and 

 vines by italics. Annual, biennial, and perennial herbs, not 

 evergreens, are designated by the customary signs, placed 

 immediately after the names. Perennial woody fungi are 

 distinguished by small capitals. Parasites are placed in 



1 The germ of this idea was taken from J. W. Blankinship's paper on 

 the plant formations of Eastern Massachusetts, in Rhodora for May, 1903. 



9 In the case of a few species which are partly evergreen the generic- 

 name is printed in ordinary and the specific in heavy type. 



