GOLD COAST REPORT OX FORESTS. 149 



procured, aud reliable averages for intermediate conditions of 

 the soil can then be reached by estimation. Of course, very 

 careful records will have to be kept of the measurements, and 

 each tree marked with a distinctive number by which it can be 

 identified, both in the forest and amongst the records. 



The necessity for carrying out these observations on trees that 

 are not likely to be cut or damaged during the periods for which 

 the experiments are to hold good is obvious. 



Other methods of ascertaining the rate of growth are, in the 

 case -of tropical trees, not so accurate as that mentioned above. 

 The usual one of counting the number of rings in the wood and 

 calculating the growth from the data so obtained is only accurate 

 when it is known for certain whether the rings are annual, or 

 bear some definite proportion to the age of the tree. 



As a general rule, trees with the deciduous habit strongly 

 pronounced at regularly occurring intervals, such as the dry 

 season in the case of species inhabiting the mixed evergreen 

 and deciduous forests, show well-marked differences in the 

 appearance of the tissues formed during the dry and wet periods 

 of the year, and these differences can be utilized in calculating 

 the rate of growth. 



Evergreen trees sometimes show the same regularity of differ- 

 ence, but there is in their case no means of ascertaining whether 

 it is an annual occurrence or not, unless a check depending on 

 historical information regarding the actual age of the tree is 

 available. 



A safer method is to compare the number of rings in the wood 

 of young trees with the age of the trees as estimated from other 

 evidence, such as the number of years that may have elapsed 

 since the area on which the young plants are growing was last 

 cleared by the natives for farming purposes, and the time that 

 has passed since the farm was abandoned as fallow land. 



If the average number of rings, as shown on the wood of a 

 large number of young plants, agrees pretty closely with the 

 number of years estimated from the evidence of the natives 

 regarding the period that lias elapsed since the farm was 

 abandoned by them, then it may be assumed with safety that 

 the rings in such instances are of animal growth. Similarly, 

 the correspondence between the rings and the age can be ascer- 

 tained from planted trees the ages of which are known. It may 

 happen that the average number of rings is some exact multiple 

 of the age ascertained from other evidence ; the inference then is 

 that two or more rings, as the case may be, are put on annually 

 by the tree, and such data will be sufficient for ascertaining the 

 age of the latter from an enumeration of the rings alone. The 

 correspondence between the rings and the age having been found, 

 then the age of any particular plant of the same species can be 

 ascertained by counting the number of rings along two or three 

 selected radii of a log or stump, and taking the average. 



The rate of growth is got by counting the number of rings that 

 occur along each inch of radius. In the same manner the rate 

 of growth at the different periods of life of the tree can be found. 



