MEETING OF THE BRITISH ASSOCIATION. 25 
equal extent and similar superficies, Dr. Hooker showed how extremely 
different its flora was, whether as regards the peculiarity of its genera 
and species and varieties, or their distribution over the group. 
Commenting upon the peculiarities of the flora, Dr. Hooker selected 
the rare, peculiar, and isolated forms, as the most suggestive of specu- 
lations, in which no intelligent man could resist indulging, — whether* 
for instance, these are original creations, or have originated by varia- 
tion operating through countless ages ; and whether they are newly 
developed forms, likely to increase and multiply, or very old forms 
dying out. He showed that the latter was the most probable, on va- 
rious independent considerations, and suggested, as a principal cause, 
subsidences of the land. Subsidence acts by contracting the area, and 
by intensifying the struggle for existence, but chiefly by reducing the 
number of insects which are the fertilizing agents, and especially the 
winged kinds, which are almost exclusively operative; adding that 
Mr. Wollaston had proved that in Madeira winged insects existed in 
wonderfully smaller proportion than wingless, as contrasted with the 
continent of Europe, — a conclusion that Dr. Hooker extended to other 
oceanic islets that he had visited. With regard to Madeira, however, 
man had been a more destructive agent than subsidence, for the island 
was, when discovered, so densely wooded that the settlers set fire to 
the forest, and the fire raged seven years, no doubt exterminating 
many species, and reducing the number of others proportionately. In 
the case of Porto Santo, rabbits had proved even more destructive, 
having at one time put a stop to cultivation, and fairly driven the 
settlers out of the island. 
The flora of the Canaries was next briefly sketched, and it was shown 
how analogous it was in all its main features to that of Madeira* and 
how different from the flora of Africa, to which the Canaries are adjacent. 
The Salvages rocks required special notice. They bad been visited 
recently by a very able botanist, the Rev. K. T. Lowe, who informed 
Dr. Hooker that the plants were chiefly of the Canariati type, but 
partly Madeiran. Considering their very small size and isolated posi- 
tion, this fact suggested that the Salvages are the mountain tops of a 
much larger tract of land that oucc occupied a conspicuous position 
between the Canaries and Madeira. 
The Azores are the third group of North Atlantic islets, and though 
ituated 7-AO miles from Europe, and 500 from Madeira, their flora 
