3 
1 300.J, 88 
these causes, nor any other with which, Iam, e aegnainted, will explain..the 
identity of the Ca} bse Dorenlis, Orchis viridis, and, Betuja nana, of North 
Aweriea, and of Europe; of the Potamegetons, commen. to rope and 
New Holland; of the R ot already ‘adverted io, as common to North 
America and China; of the Osmorlniza of the Himalay as, with that of. the, 
nited States ; of the wide diffusion of Samolus valerandi; and, most es- 
peal, of the een of the ciyplog ani plants fg various SP he lae aa 
whi on, 
One rather important element in all calet aes concernir ing the geo 
graphical sistabatign of Pane. is the natiial number of species upon the 
surface of the earth. In the SUNS state of herbaria, and with so many 
large distiicts, either altogether, or very imperfectly examined, there is no 
possibility of arriving at a yibirig more than al approximation to the true 
number ; and even this may preve so very wide of the truth. as to be really 
exceedingly fallacious. Nevertheless, some idea cf it may be formed from 
the following aa and conjectures : 
| Pheenogamons. |Cryptogamous, 
The capt of described Plabis in 1827, was, aeagr ding to 
Sprengel, pont 31,000 6,000 
To fea may ve he a for errors, and érroneous suppressions P 
Me 3 & 6,000 1,060 
Aaa alco ae Thdia and the Fest. of Asia et “ - 10,000 
? merica - oe - - 20,000 2,000 
“ : ’ i : : u 10,000 
setts SH R000 9,000. 
That this is not an exaggerated statement in regard America, willbe ob- 
‘vious from the following comparison of the numbers, in a few cases, of 
American species, admitte d by Spiengel, and what have since been pub- 
lished by. other botanists : 
Bes of American species ¢ 
09 thee eee to Sprengel, a according to Bentham. 
Fiviraph Ly le. ts 43 40 (74 ce 
Californizn ‘Botembniacee yi = a vi 
Habenaria &. 3L 4, “0 66 according to Lindley. 
Sertiraaestiaiy 235 fs g 633 according to De Candolle. 
410 1,146 
So that. the sepa er appears already to have been ascertained to be in 
hese seve s, nearly three times as great as Sprengel supposed. 
The best diternpt t that has yet been made to group these species Sat 
rari ras da is by Schouw, oni velit we take (Linn. vol, viii. p. 628) the 
: es : : ee 
. Ps eee Oe 2 eet 
