PROF. T. H. HUXLEY ON THE GENTIANS. 117 
who lack either the opportunity or the inclination to go through 
what they are pleased to term the drudgery of exhaustive anato- 
mical, embryological, and physiological preparation. 
Elaborate works on Distribution have been published which 
are of little more value than catalogues of reference, because 
their authors have been unaware of this necessity. And I may 
point my remarks by showing that even such a brief and im- 
perfect sketch of the minuter morphological characters of the 
Gentians as is here presented is fruitful of suggestions in regard 
to their Distribution. 
My studies of Animal Distribution have led me to the belief 
that the division of the land-surface of the globe into large areas, 
which corresponds most nearly with the broader facts, may be 
stated as follows. Europe, Africa, Asia, and North America as 
far as Mexico form one great province—Arcro@ma ; in which 
Ultra-Saharal Africa, Madagascar, Hindostan, and Indo-China 
are more or less distinctly characterized as subprovinces. For 
my present purpose it will suffice to speak collectively of the 
latter as the Southern Arctogea, in contradistinction to the rest 
ofthe province as Northern Arctogsea. South America, with the 
Isthmus, as far as Mexico, constitutes a second great province, 
AvsTRO-CoLuMBiA ; Australia with the adjacent islands a third ; 
while New Zealand and the neighbouring islets may be most 
conveniently regarded as a fourth. 
In mentioning the species of the various types of Gentianeæ 
which I have examined, I have arranged them under the heads of 
A, for Northern Arcroeza; B, AusTRo-CoLUMBIA ; C, Southern 
AzncroGza ; D, AvusTRALASIA; E, Noyo-ZELANIA. 
Adopting this scheme of four great distributional provinces, 
one of which is subdivided into two regions, the following pro- 
positions appear to me to hold good of the Gentianem :— 
1l. Species of the Order are found in all five regions. They 
flourish within the Arctic Circle and up to the limit of perpetual 
snow in mountain-ranges. They also abound in sundry tropical 
climates, both moist and dry. The Limnanthe type, represented 
exclusively by marsh- or water-plants, occurs in all the regions, 
and will not be further mentioned. 
2. The head-quarters of the Order (if we consider the number 
of types represented) are in the North Arctogeal and the Austro- 
Columbian regions, both of which contain representatives of all 
the types. 
LINN. JOURN.—BOTANY, VOL. XXIV. : L 
