502 
REVIEWS. 
or Monocotyledons, we are not prepared to say. Some of the less 
understood, but equally important peculiarities of the Flora are here 
for the first time most instructively shown; such as the prevalence of 
certain Indian genera and species, especially in the N.W. and N.E. 
coasts, and the absence of others (as] Dipterocarpese), which abound 
on some of the neighbouring Malayan Islands. 
Of the Orders, all but two (Tremandrese and Stackhousise) are 
Indian, and indeed one species of the latter is found in the Philippine 
Islands ; and but one Order (Tremandrese) is wholly endemic. No less 
than 15 of the 39 Orders are British, and 25 are European ; whilst of 
the genera upwards of 140 are Indian, and include no less than 120 
Indian species. Of the genera 50 are European with about 20 species, 
of which many are N orthern types and some of these confined in the 
Australian Continent to the Australian and Tasmanian Alps. These 
interesting wanderers are: 
Ranunculus aquatilis , and R. par- 
viflorus. 
Myosurus minimus. 
Nasturtium palustre. 
Rarbarea vulgaris . 
Arabis glabra. 
Cardamine Mrsuta. 
Draba muralis. 
Capsella procumbens. 
Senebiera didyma. 
Lepidum ruder ale. 
Stellaria glauca. 
Sygma procumbens. 
Spergularia rubra 9 
Mon tia font ana. 
Geranium dissectum. 
The other boreal genera are Anemone, Caltha, Papaver, T7ilaspi ? 
Gypsophila, Viola, Polygala, Frankenia, Elaiine, Hypericum, Fro- 
dium, Ox alls; besides a few others which, like Tribulus and Zygo- 
phyllum, extend into southern Europe, but are tropical rather than 
temperate forms. 
The above list suggests many reflections, of which the most 
attractive no doubt is that relating to the common origin, sub¬ 
sequent dispersion, and final segregation in the temperate regions of 
the Northern and Southern hemispheres of the plants enumerated. 
Of their birth-place as species nothing is yet known, whilst to 
account for their dispersion and segregation, only one theory has 
been advanced that is at the same time tenable and probable; we 
allude to Mr. Darwin’s, which assumes that these and other boreal 
forms were driven from our temperate zone into the tropical during 
the cold of the glacial epoch, and, on the return of warmth, migrated 
in opposite directions back towards the Poles, ascending the 
mountains that crossed their line of march. This is not the place 
wherein to discuss this plausible hypothesis, though it may be re¬ 
marked here that it demands a persistence of specific type through 
enormous periods, and over enormous areas, and under incalculable 
changes of conditions, that at first sight tells against Darwin’s own 
theory of the origin of species by natural selection. Plis ready 
answer would be, that though these species have not changed, others 
have; and, carrying the war into the enemy’s camp, he might thus 
quote the i Flora Australiensis ’ in his support:— 
