Islands in Favour of the Age and A rea Theory of Willis. 5 1 5 
introduction of the parent forms of these, and the long isolation both of the 
Archipelago and its separate islets. It is in accordance with generally 
accepted views to assume that the endemic species of each genus have been 
derived from parent forms originally introduced into one or more of the 
islets ; and that as the descendants of these species spread over the 
Archipelago they were exposed to different conditions in each islet, 
resulting in their varying, and in the segregation and conservation of 
different local varieties each in its own insular birthplace ; a supposition 
which is in accordance with the fact that those endemic species are really 
very local, many being confined to a single islet.* 
But Hooker held quite a different view for the origin of the 
Macaronesian species, and especially for the most typical of them, those of 
the L.aurel Woods. Whilst regarding the mass of the non-endemic species 
of the Canaries as Mediterranean plants, and the mass of the true Canarian 
endemics as derivatives of yet earlier Mediterranean types, he recognized 
a great break in the floral history of the group when, on taking a step 
farther back, he came to handle the Macaronesian species. Here he found 
the wreck of an ancient continental flora which, having been expelled from 
the continent through secular changes of climate, had 6 been preserved in 
the more equable climate and more protected area of the Atlantic Islands *. 
This view, which was elaborated in his Lecture in 1866 , was restated in 
his book on Marocco (pp. 417 , 419 ). It was based on the discovery 
of plants in the Tertiary beds of Southern Europe, closely allied to 
or identical with living Macaronesian species. 
The trend of the later evidence indicates that the Canaries and the 
Macaronesian groups generally are by no means alone in this respect, and 
that islands have often been sanctuaries for the survivors of continental 
floras that have passed away. However this may be, the view of Hooker, 
that the remains of an extinct European Tertiary flora still survive in the 
Macaronesian Islands, was combated by Grisebach in his ‘ Die Vegetation 
der Erde * (1872), but, as Engler has shown, on quite insufficient grounds. 
It was strongly supported and extended by Engler himself in his ‘ Versuch 
einer Entwickelungsgeschichte der Pflanzenwelt 5 (1879-82, i. 74 ), and had 
in the meanwhile been confirmed by later geological discoveries, notably 
those of Saporta and Marion (1876). Engler held to the position tenaciously, 
and remarked that ‘ even if we do not allow that the existing Macaronesian 
species are but slightly altered forms of species which lived in Europe in 
Tertiary times, we have sufficient other grounds for the belief that the 
endemic Macaronesian flora dates in great part from the Tertiary age and 
that the insular conditions have contributed to its preservation *. Drude, in 
his 4 Handbuch der Pflanzengeographie * (1890), deals on similar lines with 
the Tertiary character of a portion of the endemic element of the Canarian 
flora. 
