82 THE WOKLD OF LIFE 



Avhicli ^ve obtain possession, or where there are still large areas 

 of virgin forest, it would be advisable to reserve one square 

 mile in each square degree, say one in every 5000 square 

 miles. 



There are many incidental advantages in this thorough de- 

 termination of the plants growing on a definite if small area 

 over that which has usually been adopted of, as it were, skim- 

 ming the cream of the flora of enormous areas, such as most 

 of our botanical collectors have been obliged to adopt. The 

 first advantage is that the census of species in each of the 

 reserved areas can be easily made exhaustive, and therefore 

 comparable with other similar reserves. Then, when a few 

 well-chosen " reserves " are similarly treated, the change of 

 species in each degree of latitude and longitude can also be 

 determined with considerable accuracv. In like manner the 

 change of species for each 1000 or 500 feet of elevation can 

 also be found. Again, the proportion of forest trees to the 

 whole of the flowering plants in each locality will enable the 

 whole flora of a large district to be determined as to numbers 

 by ascertaining the number of species of trees only in a few 

 small areas. 



As an illustration of this mode of computation Dr. Koorders 

 has found that on the Pangerango mountain the trees form 

 one-fifth of the whole flora, while on Kambangan Island they 

 form one-fourth. If there are, as Dr. Koorders tells me, 

 about 1200 species of trees actually found in Java, and if, 

 on account of the eastern part of the island having much less 

 lowland forest, we take one-fifth as the more probable pro- 

 portion for the whole, then the flora of Java may be estimated 

 at a minimum of 6000 species; and if the number of the 

 trees is found to be greater, then at a proportionately higher 

 number. Hence it is very important that in each local flora 

 the number of its trees, shrubs, and herbs should be separately 

 given. It appears that a forest reserve of 17 square miles 

 has been established on the Bay of Manilla ; but, as it is as 

 yet very imperfectly explored, it would be more useful to 



