I 



CKOtlKAI'II V AXl) N'EGKTATinX OF XOKTTIKRX FT.ORinA. I JtJ 



3. I he boundaries of the regions may noi liave been accurately located 

 in everj- case, and thus species may be included in some of the lists which do 

 not properly belong there; just as in analyzing a mineral or ore, fragments of 

 other minerals associated with it may be included. Errors of this kind are 

 least in the largest regions, and those in which many notes have been taken 

 near their centers, well away from neighboring regions. 



4. For some of the regions, especially the smaller ones, my observations 

 have been too fe^' to make the plant lists reasonably complete and the iptr- 

 centages sufficiently accurate. In such cases the percentage figures are omitted 

 entirely, but the approximate relative abundance is indicated by the sequence, 

 as in all other cases. 



5. Mj' practice of taking notes from the car-window and on hurried 

 journeys on foot tends to show relative frequency rather than relative abun- 

 dance ; for if I saw ten specimens of a certain tree in every mile for ten miles 

 and a thousand specimens of another in one mile and no more for ten miles 

 the former would figure more largely in the returns. But such extreme cases 

 are unusual and likely to counterbalance each other to a considerable extent 

 in the long run; and besides the discreiiancies are not so objectionable when 

 bulk is taken into consideration, as is attempted here. 



6. Some of the herbs are quite conspicuous when in bloom and very- 

 inconspicuous or practically invisible at other times, so that notes made in the 

 same region at different seasons may dit¥er considerably. But at the begin- 

 ning of every list the months in which the observations were made are given, 

 so that the reader, especially if he is familiar with the flora, may form some 

 idea of its completeness. Of course the herbs that are recognizable any 

 day in the year, such as Spanish moss and wire-grass, will figure more largely 

 in the returns than those that disappear in summer or winter, and there 

 seems to be no obvious remedy for this. Shrubs and vines are affected less by 

 this seasonal error than herbs, and trees, especially evergreens, very little. 



7. Some of the herbs are so small that they cannot be seen at all from 

 a moving train. But every region has been explored on foot more or less, 

 so that few species of flowering plants have been overlooked entirely mere- 

 Ij- on account of their size ; and where bulk is the primary consideration, as it 

 is here, it is right and proper that the smallest plants should have the lowest 

 percentages. 



8. Some species are diflicult to identify at sight, especially when one is 

 traveling thirty miles an hour, and some of my identifications may be wholly 

 erroneous, for this and other reasons. Some errors of this sort, however, can 

 be checked up afterwards by what is known of the distribution, lial)itat, time 

 of flowering, etc., of the species in question ; and even where they are not 

 corrected they do not affect the statistics of the proportions of evergreens, 

 grasses, Leguminosae, etc., for it is not likely that I have mistaken the fainily 

 of plants in any case. Of course to be sure of the identity of every plant, 

 specimens should be collected for study and comparison, but that sort of work 

 consumes much more time than it is usually worth. Those parts of the coun- 

 try where botanists are most particular about the correct identification of 

 plants are generally those where the least, progress has been made along 

 phytogeographical lines.* 



*In this connection see Bull. Am. Geog. Soc. 45:41 (middle paragraph). 

 1913. 



