4 2 GE O G E Á P U I C A L DISTEIBUTION.
t h e forms characteristic of the present Intermediate Flora should therefore be largel y of
C i r c u m p o l a r type. As, h owe v e r , the natural condi t ions to which they have been subjected
a r e such as pass into t h o s e favourable for a n advance of the Equatorial Flora, a tendency
t o the zonal distribution characteristic of an advancing flora has been imparted to it.'
B r i e f l y stated, the condition of afíairs has always been this:—the constituents of the
Intermediate Flora during each period of approximat e equilibrium have been mainly
d e r i v a t e s of the flora that retreated during the migration immediately preceding in
d i s t r i b u t i o n parallel t o the constituents of the flora that advanced during the same time.
T h e general agreement of the distribution of Fodieidaris with this hypothesi s becomes
v e r y evident whe n table V I given above (p. 25) is replaced by a diagram in which the
e n d e m i c percentages are shown
DIAGRAM 2K
' If the hypothesis be correct, the forms characteristic of the Southern Intermediate Flora should cTideace their residual
character by beiflg of Equatorial type, and as physiographical cireumstances have protected them from pressure on the part of
an ftdTancing southern Circnmpolar Flora during the most recent migration, their forms should exliibit a meridional rather
than a zonal distribution. We should eipoct, for insUnce, to find in South Africa that kteral distribution-e.j. the
appearance of the same species in Western Cape Colony and in Natal—is a somewhat exceptional phenomenon. This does
not, however, affect the constitution of tho genus under discussion.
» This diagram and the nine that succeed it are uniform and have been constructed on the following principle Tie
t e n t r e of the circle that represents the Arctic province coincides with the North Pole, while the lentro of each of tho other
iireleB coincides with the ccntre of area on a map of the Northern Hemisphere of cach of the individual provinces ; the area
of each circle is at the same time in direct proportion (o the total Lumber of species of Fedicularis reported from the
province that the circle represents—an arbitrary area being of course choMn for one proTince, the others being made to
conform to the first.
MERIDIANS OF DISTRIBUTION.
4 3
T h i s diagram appears to prove—
n i that there are four meridians of distribution passing from the Circumpolar
p r o v i n c e to the American, European, Siberian, and Japanese provinces
r e s p e c t i v e l y ; '
( 2 ) that there is no extension of the American or European meridians ; and
( 3 ) that the Siberian mer idian is projected into the Caucasus.
A t t h e s ame t ime it i t doubt ful —
( 1 ) whether the Tibeto-Chinese province may be a project ion of the Japanese
m e r i d i a n of distribution or be due to a bifurcation of the Siberian
m e r i d i a n within t h a t province ; and
( 2 ) whether the Himalaya-Yunnan province may be a projection of the Tibeto-
C h i n e s e meridian (whatever its derivation) or be a projection of the
m e r i d i a n of distribution through the Caucasus.
B u t as these points of dubiety only raise questions of possible alternative interp
r e t a t i o n and do not assaH t h e truth of the general position, we are at liberty t o proceed
a t once to a consideration of the special evidence from structure and, in indicating how
f a r it is corroborat ive of tlie general arithmetical evidence, to not e at wha t points and
i n wha t direction these doubtful problems are solved.
' The reader will bear in mind that Sir J . D. Hooker (Trans. Linn. Soc. sxiii) has shown the possibility of there having
been a meridian of distribution along Greenland, and that this meridian, at all events daring the last southward migration,
may have terminated in tho ciU-de-sac which its present physiography would suggest. The morphological evidence of
Pediciilaris having already declared the whole of G-reonland to be at present circumpolsr is not available as a test of this.
Sir J . D. Hooker has also shewn in the same place that tho flora of Greenland haa very much greater Lapponic than American
affinities while Baffin Bay and Davis Strait indicate a sharper cleaTage line than the ocean between East Greenland and
Norway. It is interesting to obserre that, so far as tho evidence from Pedicularis is concerned, there is, in spite of tho present
continuity of Arctie-Alpina conditions, as sharp a cleavage between America as a whole and Alaska, for of the twelve
Alaskan species, only two—-P. eaphranoides and P. ¿jaZtwir»i—pass to America, while the significance of this distribution is
extremely slight since both these species are examples, as their zonal distribution testifies, of the Temperate-Intermediate
and not of tho Arctic-Alpine Circumpolar Flora. This cleavage is confirmed by the evidence of P . sadelica, which on the
European and on the Siberian meridians of distribution remains undistinguishable from the Arctic plant, but has on the
American meridian been modified into a perfectly distinct, although still representative species, P. scopaloram. Besides the
negative evidence as regards the American meridian, there is positive evidence as regards the adjacent Japan-China-
Himalaya meridian. One species {P. Chamissonis) is confined to this meridian, extending along it to Japan. Two others—
P . veHicillata and P. Oeifli-i-appear in Northern Cliiaa. At the same time one of the endemic species, P. pedicillata,
has its nearest allies in Chinese and European species, and the other, P . Afonisesit, is (like P . verlieillata) distinctly separated
from all the species of the American meridian by its character of opposite leaves—a character which does not occur among
American species proper, but is, on the other hand, highly characteristic of tlie Japan-China meridian.
The cleavage between Alaska and Greenland pointed out by Sir J . D. Hooker is strikingly verified b y tho evidence from
this genus. While ten Alaskan species, or 83i per cent., occur in Arctic Asia, only three (P. eup/tranoides, P. kirsuta, and
P . lanaia), or 25 per cent., occur in Greenland. The evidence of P. cnphriuioides has to be discounted, and though there is
no evidence that the extension is not direct in both the other cases, there is proof in one case that it need not be. 1-or while
P . lanata is confined to Easter n Arctic Asia, Alaska, and Greenland, P . hirsuta extends from Alaska through the whole of
Arctic Asia and Europe to Lapland, and it may well be in this direction that its extension into Greenland is to be
sought for.
But while the cleavage between Greenland and Alaska is thus borne out, the genus affords no evidence of a cleavage
between Greenland and the rest of America. It appears on the contrary to indicate that the American province and Greenland
are on the same meridian of distribution. For while of the sis species that occur in Greenland, three (P. hirsuta, P. lapponica,
and P . flammea), or 60 per cent., extend to Lapland, and three (P. kirsuta, P. lanaia, and P . euphrasioides), or 60 per cent., to
Alaska, four, or 08^ per cent..pass across Davis Strait: two of these indeed (P.Jlammca and P. lapponica) no fnrttier than
to Labrador, thus remaining circumpolar, but the other two (P. euphrasioides and P. groenlandica) into the American
ANK. EOY. BOT. GARD. CALCUTTA, YOL. III.