166 Part IL. Chapter 3. 
Chapter III. Statistics of North American Plants, 
The number of species of plants in North America can be stated only 
approximately, because the total is subject to change with the exploration of 
territory unknown botanically and with the advance of our knowledge as to 
the systematic relationship of plant species. For the United States and 
Canada, we have fairly accurate data, but for Mexico, Central America 
and the West Indies, we can make only an estimate, because these tropic 
countries are still too little known. There is a tendency manifested among 
American botanists to multiply species, it seems to the writer to an undue 
extent. For example in the two years 1898 to 1900 about 2000 new plants 
names were published, representing dona fide new plants, but in addition the 
reinstatement of names established by NUTTALL, PURSH and other botanists, 
who were actually acquainted with the plants, they described and whose 
names were suppressed by later botanists less familiar with the plants as they 
occur in the fields and forests. There is a growing disposition to discard the 
use of varietal names, and to call all plants species which have characters 
sufficiently distinct to justify the use of a specific name. Accordingly, many 
varieties have been raised to specific rank. At the present rate of activity in 
systematic botany, the year 1908 will see a list of about 22,000 American 
plant names. HELLER (1900) in his Catalogue of North American Plants, 
North of Mexico, exclusive of the lower cryptogams enumerates 16,673 plants. 
SERENO WATSON in the sixth edition of GRAY’s Manual (1890) which classi- 
fies the plants of the northern United States, including the district east of the 
ıooth meridian and north of North Carolina and Tennessee, gives a list of 
orders with the number of genera and species native and introduced. He 
enumerates 251 native and 46 introduced genera and 777 native species; 141 
introduced species of apopetalous dicotyledonous plants. Of gamopetalous 
plants, there are 245 native genera, 53 introduced genera, 874 native species 
Ieor. ei introduced Species within the region covered by the manual. The 
pe alous dicotyledons comprise 76 native genera, 7 introduced genera, 257 
native species and 51 introduced. The conifers consist of ı0 native genefa 
ur ee Of monocotyledonous plants there are ı70 native genefä, 
: „genera, 721 native species and 64 introduced species. The 
pteridophytes include 29 native genera with 103 native species, and the bryo- 
phytes 44 native genera, ı introduced genus, 140 native And ı introduced 
Gr introduced lan ann a Of Bis genera of native, 129 geiE 
» 2093 native species and 405 introduced species 0 
plants; total 963 genera and 3298 species of plants. 
be er of ER New Manual of Botany (1908, ost 
total number ör diklerene En ee u Sn d in 
(he fein a u (species, Yarleties and named forms) foun llel 
9oth meridian of longitude, south of the 48th paralle 
